1. health and fitness
2. disease
3. asthma

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GUIDELINES
Canadian guidelines for the management of acute
exacerbations of chronic bronchitis
Meyer S Balter MD FRCPC1, Jacques La Forge MD FRCPC CSPQ2, Donald E Low MD FRCPC1,3,
Lionel Mandell MD FRCPC4, Ronald F Grossman MD FRCPC FACP1 and the Chronic Bronchitis Working Group5
on behalf of the Canadian Thoracic Society and the Canadian Infectious Disease Society
MS Balter, J La Forge, DE Low, L Mandell, RF Grossman,
and the Chronic Bronchitis Working Group on behalf of
the Canadian Thoracic Society and the Canadian
Infectious Disease Society. Canadian guidelines for the
management of acute exacerbations of chronic bronchitis.
Can Respir J 2003;10(Suppl B):3B-32B.
Acute exacerbations of chronic bronchitis (AECB) account for over
1.5 million physician visits annually in Canada and are a cause of significant morbidity and mortality. This document represents a joint
effort between respirologists, microbiologists, infectious disease specialists and family physicians to update the Canadian AECB guidelines published in 1994. Treatment recommendations are graded on
the strength of evidence in the published literature where possible.
The role for oral corticosteroid therapy in preventing treatment failures, speeding up recovery and delaying the time to next exacerbation is discussed. Risk factors for treatment failure were used to
stratify patients into risk groups to help guide antibiotic treatment
recommendations. The importance of emerging antimicrobial resistance to current antibiotics is reviewed and strategies to prevent
future AECB episodes are suggested.
Lignes directrices canadiennes sur le traitement des exacerbations aiguës de bronchite
chronique
Les exacerbations aiguës de bronchite chronique (EABC) motivent plus
1,5 million de consultations médicales chaque année, au Canada et sont
cause d’une morbidité et d’une mortalité importantes. Le présent document est le fruit du travail de collaboration entre les pneumologues, les
microbiologistes, les infectiologues et les omnipraticiens visant à actual
iser les lignes directrices canadiennes en matière d’EABC, publiées en
1994. Les recommandations relatives au traitement ont été cotées, dans la
mesure du possible, en fonction du degré de fiabilité des données trouvées
dans la documentation. On y traite du rôle de la corticothérapie orale
pour éviter les échecs de traitement, accélérer le rétablissement et
repousser la prochaine exacerbation. Les facteurs de risque d’échec de
traitement ont servi de critère à la classification des patients en groupes de
risque pour aider à orienter les recommandations quant à l’antibiothérapie. Il est également question de l’importance d’un phénomène nouveau, soit de la résistance des bactéries aux antibiotiques actuels, et de
stratégies pour prévenir les futurs épisodes d’EABC.
Key Words: Chronic bronchitis, Exacerbations, Antibiotics, Risk
Stratification
cute exacerbations of chronic bronchitis (AECB)
account for over 1.5 million physician visits annually in
Canada and are a cause of significant morbidity and mortality. Canadian guidelines for the management of chronic bronchitis were published in 1994 (1). In that document, the
pathophysiology of chronic bronchitis and emphysema and
the pathology, risk factors, diagnosis and treatment of chronic bronchitis were discussed. AECB were dealt with in the
major section of the document. A stratification system comprising five different patient groups was proposed, with
antimicrobial recommendations made for each group. Many
recent developments have forced a re-examination of these
recommendations with respect to the risk stratification process
and the specific antimicrobial recommendations. This document is an update from our original guidelines and is a joint
effort by the Canadian Thoracic Society (CTS) and the
Canadian Infectious Disease Society (CIDS).
A
METHODS
A needs assessment survey was sent out with the 1994 guidelines
to representative family physicians across Canada early in 1999.
The purpose was to obtain insight into the major challenges they
faced in diagnosing and managing AECB. A committee was established that was composed of members from both the CTS and the
CIDS, as well as two family physicians with strong interests in
continuing medical education and AECB. The committee members were divided into four teams, each of which was responsible
for one of four sections. These sections were as follows: epidemiology, risk factors, pathogenesis and pathophysiology; diagnosis
and therapy excluding antibiotics; antimicrobial therapy; and
resistance. The committee met for one day in Toronto, Ontario, in
May 1999 to discuss key areas of interest and controversy.
Subsequently, each team developed a draft of its section. These
drafts were then circulated among all committee members and
revised a number of times based on comments from committee
members and outside reviewers.
1University
of Toronto, Mount Sinai Hospital, Toronto, Ontario; 2Laval University, Hôpital Laval, Ste-Foy, Quebec; 3The Toronto Hospital,
Toronto Medical Laboratories, Toronto, Ontario; 4McMaster University, Henderson General Hospital, Hamilton, Ontario; 5See appendix
Correspondence: Dr Meyer Balter, 640-600 University Avenue, Toronto, Ontario M5G 1X5. Telephone 416-586-4663, fax 416-586-4736,
e-mail mbalter@mtsinai.on.ca
Reprints: Core Health Services Inc, 1800 Steeles Avenue West, Second Floor, Concord, Ontario L4K 2P3
Can Respir J Vol 10 Suppl B July/August 2003
©2003 Pulsus Group Inc. All rights reserved
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Relevant articles published between 1966 and July 1, 2002,
were retrieved from Medline using the index terms ‘chronic
obstructive pulmonary disease’, ‘chronic bronchitis’ combined
with ‘acute exacerbations’, as well as specific terms relating to various interventions such as ‘steroids’, ‘bronchodilators’, ‘anticholinergics’, ‘antibiotics’ and ‘mucolytics’. Articles published before
1966 were retrieved from the reference lists of later papers. The
Cochrane control trials register until the end of the year 2001 was
also searched. In addition, abstracts from the American Thoracic
Society, American College of Chest Physicians, European
Respiratory Society and International Conference on
Antimicrobial Agents in Chemotherapy meetings from 1999 to
2002 were reviewed.
Treatment recommendations were graded on the strength of
evidence similar to those used for the Canadian guidelines for the
initial management of community-acquired pneumonia (2). Wellconducted, randomized, controlled trials constitute strong or
Level I evidence; well-designed controlled trials without randomization including cohort and case-control studies constitute Level
II or fair evidence; and expert opinion, case studies, and before
and after studies are Level III or weak evidence. These ratings
appear as roman numerals in parentheses after each recommendation in these guidelines.
EPIDEMIOLOGY AND RISK FACTORS
Chronic obstructive pulmonary disease (COPD) is now the
fifth leading cause of death in Canada and the prevalence is
increasing (3). There have been several attempts in recent
years to define COPD (4,5). Most definitions consider COPD
to be a disease state characterized by air flow limitation that is
not fully reversible. The air flow limitation is usually progressive and associated with an abnormal inflammatory response of
the lungs to inhaled particles or gases. It is an umbrella term
that includes the entities of chronic bronchitis and emphysema
when associated with air flow limitation. Ordinarily, asthma,
cystic fibrosis, bronchiectasis and bronchiolitis obliterans are
excluded from this definition.
Chronic bronchitis can be defined clinically as a disorder
with expectoration of sputum on most days during at least
three consecutive months for more than two successive years,
other causes of cough and sputum having been excluded (6).
Chronic bronchitis is present in approximately 85% of patients
with COPD. Chronic bronchitis frequently coexists with
emphysema and small airways disease, the degree of each varying from person to person. It is essential to recognize that
chronic bronchitis often occurs without airway obstruction;
only a minority of patients with chronic bronchitis have evidence of COPD (7).
Epidemiology
Between 1951 and 1984, the mortality from COPD in Canada
increased in both sexes, and by the mid 1980s, COPD was the
sixth leading cause of death in men and the eighth leading
cause of death in women (8). By 1995, COPD was the fifth
leading cause of death in Canada and there had been an
increase in total deaths from 4438 in 1980 to 8583 in 1995.
During this period, the age-standardized mortality in men
remained stable (around 45 per 100,000 population) while it
doubled in women (8.3 per 100,000 in 1980 to 17.3 per
100,000 in 1995) (9). Review of data from the 1994 to 1995
Canadian National Health Survey indicated that about
750,000 Canadians had chronic bronchitis or emphysema
4B
diagnosed by a health professional. The prevalence of COPD
in Canada has been estimated to be about 5% in adults
between the ages of 55 and 75 and approximately 7% in the
over 75 age group. In 1993 to 1994, there were 55,782 hospital
separations in which COPD was the primary discharge diagnosis; this was increased from 42,102 in 1981 to 1982. The average in-hospital length of stay for patients admitted with COPD
was 9.6 days in 1981 to 1982 and 8.3 days in 1993 to 1994 (9).
These data clearly demonstrate that COPD is a disorder with
enormous morbidity and mortality, and puts a very significant
burden on health care resources.
COPD appears to have a similar prevalence in other
Western countries. The Cardiovascular Health Study (10) in
the United States, in which spirometry was performed on 5201
elderly individuals, demonstrated that 5% of adults over the
age of 65 reported a diagnosis of one of the COPDs (asthma,
chronic bronchitis and emphysema). In this study, undiagnosed airway obstruction was noted in 7% of individuals and
was most likely to occur in current and former smokers,
women, lower income groups and individuals with chronic
cough. This still may be an underestimate with reports of as
many as 20% of the population having COPD in the United
States, where it is the fourth leading cause of death (11,12).
The prevalence of COPD in Europe varies from approximately
4% in Denmark and Norway (13,14), to 6% in Spain and
Sweden (15,16). Data from the Asia Pacific area appear to be
in the same range (17). In some communities, the prevalence
of chronic bronchitis is much higher, and this may reflect the
local environment and smoking habits. In Nepal, the prevalence of chronic bronchitis is 18% with similar frequency in
men and women, and this may relate to exposure to wood
smoke for cooking with inadequate or absent ventilation (18).
Risk factors
Smoking, some occupational exposures and alpha-1 antitrypsin deficiency are well-established risk factors for the
development of COPD. There is good evidence that a number
of other risk factors are also important including air pollution,
environmental tobacco smoke, respiratory infections, airway
hyperresponsiveness and genetic factors.
Cigarette smoking is undoubtedly the most common cause
of chronic bronchitis, and there is well-established evidence
that cigarette smoking is associated with increased mortality
from COPD, increased prevalence of symptoms of COPD and
increased prevalence of lung function abnormalities. The
degree of abnormality is proportional to the amount smoked
and is not specific for cigarettes, because both pipe and cigar
smokers also have an increased morbidity and mortality from
COPD. Although many smokers have some degree of cough
and sputum production, only approximately 15% will develop
significant COPD (19-21). In Western society, cigarette smoking accounts for 80% to 90% of the overall COPD burden (22).
A number of occupations have been associated with the
development of COPD, and there is good evidence that chronic
exposure to cadmium, silica, minerals and grain dusts can
result in the development of airway disease. Workers involved
in mining, furnace work, farming, metal work, wood and paper
work, and cement workers are all at increased risk. Grain workers and cotton workers also have an increased risk of COPD
(23,24).
Alpha-1 antitrypsin deficiency is a well-recognized cause of
COPD but is responsible for less than 1% of all cases. Only a
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few nonsmokers with alpha-1 antitrypsin deficiency develop
emphysema; most never develop symptoms. Some alpha-1
antitrypsin-deficient smokers never develop obstruction (25).
Some families appear to have an increased risk of COPD and it
is probable that other genetic factors may increase susceptibility
to COPD (26).
Individuals with increased airway hyperresponsiveness who
smoke appear to be at increased risk for the development of
COPD. It is difficult to determine whether bronchial hyperresponsiveness is a true risk factor for COPD or whether it follows as a result of the development of smoking-related airway
disease and the decrease in lung function. The Lung Health
Study demonstrated a strong correlation between increased
bronchial hyperresponsiveness and accelerated decline in
forced expiratory volume in one second (FEV1) (27). This
finding confirmed earlier work that showed that both smokers
and exsmokers with less nonspecific hyperreactivity had a
slower decline in FEV1 (28).
Ongoing exposure to environmental tobacco smoke and
secondhand smoke appears to be a risk factor for the subsequent development of chronic bronchitis (29); 4197 never
smokers aged between 18 and 60 years in eight separate geographic areas of Switzerland were surveyed and it was found
that there was an increased prevalence of respiratory symptoms
that was directly proportional to the increased dose and duration of exposure to secondhand cigarette smoke (30).
There appears to be a causal relationship between early
childhood infections and respiratory symptoms and reduced
lung function in adult life. Over 800 children in East Boston
were observed for 13 years, and it was found that respiratory illness before two years of age and two or more lower respiratory
tract illnesses during a single surveillance year were associated
with lowered lung function in adulthood (31). The causal relationship between pneumonia in early childhood and COPD in
late adult life has been further supported in a study of 618 subjects with a mean age of 70 years in whom parish records were
available for their first two years of life. It was found that pneumonia before the age of two was associated with a lower FEV1
in late adult life (32). Adenoviral infections are responsible for
many childhood respiratory illnesses and the adenovirus is
known to persist in a latent form. Latent adenoviral DNA was
more commonly found in individuals with COPD than in
those without (33). These data suggest that the developing airways are vulnerable to the effects of infection, and that latent
adenoviral infections may contribute to the pathogenesis of
COPD in adults. The role of acute respiratory infections in
adults is less clear, although there is a good theoretical argument to support the “vicious circle” hypothesis of Cole and
Wilson (34) that ongoing chronic bacterial infection may
result in ongoing airway damage.
Air pollution appears to be a significant risk factor for
COPD. The risk appears to be related to the nature and intensity of the air pollution. Exposure to particulates less than
10 microns was strongly correlated with the development of
cough and sputum production and mortality in the Utah valley
(35). More recently, a direct association between exposure to
particulates in the air in Switzerland and symptoms of chronic
phlegm production and cough was demonstrated in a large
population study (36). Levels of air pollution have fallen considerably in most developed countries but are still high in
many cities in developing countries, and levels of indoor air
pollution can be very high in these countries – in particular,
Can Respir J Vol 10 Suppl B July/August 2003
where wood is burned to cook and heat the home. A recent
case-control study in Colombia found wood smoke to be more
highly associated with the development of COPD in women
than either tobacco use or passive smoking (37).
There is currently no good evidence that race, socioeconomic class, education and dietary factors can be linked definitively as independent risk factors to the development of
COPD. Recent data suggest that female sex may be an independent risk factor, although this has not been clearly established (38). It appears that women have a higher prevalence of
airway hyperreactivity than men (39). Whether this alone
explains their apparent increased susceptibility to the harmful
effects of cigarette smoking remains to be determined.
PATHOGENESIS, PATHOLOGY AND
PATHOPHYSIOLOGY
The past few years have brought with them new interest into
the basic mechanisms contributing to chronic bronchitis. A
detailed review of this topic is outside the scope of these guidelines and the interested reader is referred elsewhere (40,41).
This section reviews some basic tenets regarding the pathogenesis, pathology and pathophysiology of chronic bronchitis, particularly as it relates to acute exacerbations of the disease.
The pathological lesions of chronic bronchitis involve both
the large and the small airways. The walls of the airways of
affected patients contain a prominent inflammatory cell infiltrate. In the large airways, this inflammatory process is associated with metaplasia of both the columnar and the goblet cells
lining the epithelium, an increase in the size of the mucoussecreting glands (42), an increase in the amount of smooth
muscle and connective tissue in the bronchial wall (43) and
degeneration of the airway cartilage (44). The Reid index, a
ratio of gland to bronchial wall thickness, is the pathological
marker of the excess cough and sputum production that defines
the disease (39). However, there is no relation between this
index and the degree of air flow obstruction, which appears to
correlate better with the presence of inflammation in the small
airways (45). Smooth muscle hyperplasia in chronic bronchitis
is not related to bronchodilator responsiveness or bronchial
hyperreactivity as occurs in asthma. However, bronchial
hyperreactivity can be seen in up to 50% of patients with
chronic bronchitis, occasionally making it difficult to exclude
an asthmatic component to the illness. Part of the reason for
the finding of bronchial hyperreactivity in chronic bronchitis
may be due to the fact that these patients are starting with a
lower FEV1. The lower the FEV1, the greater the response to
an inhaled bronchoconstrictor. Therefore, the relevance of
this finding remains unclear.
Two separate hypotheses have been put forward to explain
the pathogenesis of chronic bronchitis and COPD. The
“Dutch hypothesis” (46) postulated that airway hyperresponsiveness and atopy were markers of a basic genetic disturbance
predisposing to the development of chronic lung disease characterized by the presence of cough, sputum production and
air flow limitation. This suggests that asthma and chronic
bronchitis are variations of the same disease. The “British
hypothesis” (47,48) proposed that chronic obstructive bronchitis develops as a result of bronchial irritation and subsequent hypertrophy of mucous-secreting glands due to smoking,
pollution and recurrent infections. The development of cough
was hypothesized to lead to progressive airway obstruction, disability and death. A major criticism of this hypothesis was the
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lack of evidence linking chronic cough and sputum production
to progressive air flow limitation (49-51). However, recent studies have shown a consistent association between chronic
mucous hypersecretion and both an accelerated decline in FEV1
and an increased risk of subsequent hospitalization
(52-54). In addition, exacerbation frequently appears to be correlated with FEV1 decline (55), particularly in patients who
continue to smoke (56). Thus, it appears that components of
both of these hypotheses are likely to be correct. This would
make it easier to explain the pathogenesis of such a heterogeneous disease.
The inflammatory cell infiltrate affects both the central airways and the peripheral airways, the sites responsible for the air
flow limitation in smokers. So called ‘small airways disease’, a
chronic inflammatory process of the small airways, has been
demonstrated in virtually all young smokers (57). In addition,
increased peripheral airway inflammation distinguishes the airways of smokers with obstruction from those without obstruction (58). However, only 15% to 20% of heavy smokers go on
to develop clinically significant or measurable airway obstruction (48,59). Therefore, factors other then cigarette smoking
alone must contribute to the development of air flow obstruction. There are most likely genetic factors influencing the susceptibility to the effects of cigarette smoking or the
development of the airway inflammatory response to various
stimuli (60,61). The association of mucous gland enlargement
and goblet cell hyperplasia with the intensity of the inflammatory cell infiltrate in airway walls also suggests that inflammation is of central importance in the pathogenesis of chronic
bronchitis. However, the cells, cytokines and mediators
involved in the airway inflammation of chronic bronchitis are
quite different from those found in asthmatic airways, perhaps
explaining the differences in clinical presentation and responses
to treatment of these diseases.
The neutrophil is the predominant cell found in the airways
of patients with chronic bronchitis. Bronchial lavage fluid
from patients with chronic bronchitis contains a significantly
higher percentage of neutrophils than lavage fluid from asymptomatic smokers or normal control subjects (62). In addition,
the potent neutrophil chemotactic factors, interleukin (IL)-8
and leukotriene B4 (LTB4), and the neutrophil activation
products myeloperoxidase (MPO) and elastase, are elevated in
chronic bronchitis (63-65). There is evidence that the bacteria
that colonize the airways of patients with chronic bronchitis
and that are involved in many of the exacerbations of the disease secrete products that contribute to this neutrophil-driven
inflammation (66). A higher percentage of neutrophils was
found in the airways of smokers who developed airway obstruction over a 15-year period than those who did not (67). In
addition, the annual decline in FEV1 over the15-year period
was related to the degree of induced sputum neutrophilia
implying cause and effect (68). Patients with more severe air
flow obstruction have a higher percentage of neutrophils in
both induced sputum and bronchial lavage (62,68,69). Finally,
neutrophils in induced sputum are higher in COPD patients
with severe air flow obstruction than nonobstructed smokers,
nonsmoking control subjects and asthmatics (69).
Macrophages and activated T lymphocytes are also
increased in the airways of patients with chronic bronchitis
(70). The T cells are of the CD8+ variety, differentiating the
type of inflammation from that seen in asthma (71).
Eosinophils, which are the predominant inflammatory cells in
6B
the airways of asthmatics, do not seem to play a prominent role
in the stable chronic bronchitic patient, although there have
been reports of elevated bronchial lavage and biopsy eosinophils
in some studies (64,65,72). The eosinophil may have a more
prominent role in the pathogenesis of acute exacerbations (73).
Airway inflammation during AECB
Patients with chronic bronchitis are prone to recurrent exacerbations of their disease. Evidence is beginning to emerge that
these exacerbations are associated with increased airway
inflammation. In addition, there appears to be an association
between the degree of inflammation and the severity and frequency of the exacerbations. Both the absolute number and
the proportion of neutrophils in bronchoalveolar lavage
(BAL) increase during AECB (74). In addition, cytokines and
mediators known to reflect neutrophil infiltration and activation rise during AECB. Levels of IL-8, MPO and LTB4 in
induced sputum all rise during AECB (75-78). Patients with
higher baseline cytokine levels have more frequent exacerbations (76). Patients with severe AECB requiring hospitalization have evidence of more severe neutrophilic inflammation
during exacerbations (75).
Eosinophils, which do not appear to play a significant role
in the pathogenesis of chronic bronchitis, may be important
during AECB. There are increased numbers of eosinophils in
induced sputum and BAL during AECB (74). In addition,
bronchial biopsies taken from the airways of mild chronic
bronchitics during an acute exacerbation have revealed
marked increases in mucosal and submucosal eosinophils, as
well as evidence of increased cellular activation (73,79).
Role of bacteria in chronic bronchitis and AECB
The normal tracheobronchial tree is sterile. In patients with
chronic bronchitis, the lower airways are chronically colonized
with bacteria, predominantly Haemophilus influenzae, Moraxella
catarrhalis and Streptococcus pneumoniae (80-82). The role that
these bacteria play in causing progressive lung disease remains
controversial, but a clearer understanding of their interaction
with damaged airways is emerging.
Cigarette smoking leads to the loss of ciliated epithelium
and more viscous airway secretions, compromising the local
defenses of the respiratory tract. The delay in mucociliary clearance allows inhaled bacteria to colonize the normally sterile airways (83). Once bacteria adhere to mucin or epithelial cells in
the lower airway, they persist by further impairing mucociliary
clearance. There are several mechanisms whereby bacteria may
damage the lower airways. H influenzae, S pneumoniae and
Pseudomonas aeruginosa have all been shown to stimulate mucus
secretion (84). These same bacteria produce substances that
impair ciliary function (85,86). In addition, there is some evidence that H influenzae can directly cause airway epithelial
injury (87). Finally, bacteria residing in the lower airway secrete
enzymes that break down local immunoglobulins, and also
demonstrate antigenic heterogeneity to avoid immune surveillance and can form microcolonies surrounded by polysaccharide gel to decrease their clearance (88).
It is becoming clear that bacteria colonizing the lower
airways of patients with chronic bronchitis are capable of stimulating the secretion of various inflammatory mediators
and cytokines that contribute to airway inflammation.
Lipopolysaccharide (LPS) is the major glycolipid in the outer
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Management of AECB
membrane of Gram-negative bacteria. Bacteria colonizing the
airways are in a constant state of turnover to avoid recognition
by the host inflammatory response. As they turn over, bacteria
release extracellular products as well as LPS from their cell
walls. LPS is a very potent inflammatory stimulus. H influenzae
expresses an LPS molecule that lacks the long repeating polysaccharide side chains that are typical of this molecule in
other Gram-negative bacteria. Therefore, the endotoxin of
H influenzae is more commonly referred to as a lipo-oligosaccharide (LOS). LOS is a potent secretagogue for a variety of
inflammatory mediators. It can increase epithelial cell permeability and can lead to the release of IL-6, IL-8 and tumour
necrosis factor (TNF) (89).
Evidence has accumulated suggesting a correlation between
levels of inflammatory mediators and cytokines and bacterial
colonization of the lower airways. Soler et al (90) performed
BAL and compared quantitative cultures of bacteria in the
lower airways with the levels of various cytokines. They
demonstrated that bacterial colonization of the lower airways
was associated with significantly more neutrophils and TNFalpha when compared with airways that did not have significant amounts of bacteria. In addition, there was a trend toward
higher levels of IL-8 in the BAL of patients colonized with
bacteria. Interestingly, bacterial colonization and increased
inflammatory cells and cytokines occurred in patients with
chronic bronchitis whether or not they had associated air flow
obstruction. Bresser et al (91) performed similar experiments
using expectorated sputum in patients with both obstructive and
nonobstructive chronic bronchitis. They found similar correlations between the levels of certain cytokines and infection with
H influenzae. Of interest, they also found differences in levels of
TNF-alpha in patients with obstructive lung disease when compared with patients with nonobstructive chronic bronchitis.
This is of interest because the TNF-alpha has been implicated in
the pathogenesis of chronic airway obstruction (69,92).
To summarize, initial damage to the airways, most commonly caused by cigarette smoking, impairs mucociliary clearance and weakens host defences, allowing the normal steril
airways to become colonized with bacteria. Once the bacteria
colonize the airways, they contribute to the airway inflammation and impaired mucociliary clearance allowing their persistence in the airways and, perhaps, contributing to progressive
airway obstruction. This is referred to as the “vicious circle”
hypothesis (Figure 1) (34,93).
Lower airway bacterial colonization during the stable state
Initial studies examined the presence of bacteria in the sputum
of patients with stable chronic bronchitis. H influenzae was
present in the sputum of up to 60% of such patients (94). More
recently, bronchoscopic techniques have been used to examine
pathogens residing in the airways during stable chronic bronchitis. Cabello et al (95) found colonization of the lower airways in 83% of COPD patients. They claimed that only a
minority of these bacteria were potentially pathogenic.
However, nonpotentially pathogenic bacteria may still contribute to lower airway inflammation and risk of recurrent
infections with other species. In addition, our view as to what
is a pathogenic microorganism changes with time. For example, M catarrhalis was considered a commensal for many years
but is now thought to be a pathogenic species in AECB. A similar debate revolves around Haemophilus parainfluenzae (96).
Zalacain et al (97), using a protected specimen brush, found
Can Respir J Vol 10 Suppl B July/August 2003
Figure 1) The role of cigarette smoke and viral infection in initializing
and perpetuating the “vicious circle” of impaired local defenses. IgA
Immunoglobulin A Source: Recommendations on the Management of
Chronic Bronchitis: A Practical Guide for Canadian Physicians.
Reprinted from Supplement to CMAJ 15 November 1994; 151:7-23 by
permission of the publisher, © 1994 Canadian Medical Association (1)
significant bacterial growth in 40% of patients with stable
COPD and in none of the control subjects. Monso et al (98)
found significant bacterial growth in 22% of patients with stable COPD using similar methods. Nontypeable H influenzae
was the most common isolate in both studies, which is consistent with virtually all studies done using sputum from patients
with chronic bronchitis. Monso et al (98) reported that current smoking was the most important predictor of bacterial
colonization, whereas Zalacain et al (97) determined that air
flow obstruction and smoking were independent predictors of
airway bacterial colonization. Recent studies have confirmed
the association between the degree of air flow obstruction and
the type of bacteria colonizing the lower airways. Individuals
with chronic bronchitis and an FEV1 less than 50% of predicted have a six-fold higher risk of being colonized by virulent
Gram-negative bacteria such as P aeruginosa and
Enterobacteriaceae species than do patients with an FEV1 above
50% of predicted (99,100). Whether this is an effect of worsening air flow obstruction or, more likely, an effect of more frequent episodes of AECB with subsequent use of antibiotic
therapy in patients with poor lung function remains to be
determined.
The location of bacteria within the airways may be important in terms of both inducing inflammatory responses and
protecting the bacteria from local defense mechanisms.
Nontypeable H influenzae not only binds to human epithelial
cells in the airways but is able to penetrate the epithelial cell
layer where they may be protected from both antibiotics and
antibody mediated bactericidal activity (101,102). Moller and
colleagues (103) found H influenzae not only in the epithelium
and submucosa of the bronchi, but also in the interstitium and
alveolar epithelium of patients with end-stage lung disease
undergoing lung transplantation. These bacteria residing in
tissues may act as a reservoir for recurrent infections or induce
chronic low-grade infection that continues to enhance the
host inflammatory response as described by the vicious circle
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TABLE 1
Prevalence of bacterial pathogens from sputum in acute exacerbations of chronic bronchitis
Fogarty Eller et al
et al (106)
(99)
Wilson et al
(107)
Shah et al
(108)
Langan et al Georgopoulos
(109)
et al (110)
Habib
et al (111)
Chodosh
et al (112)
DeAbate
et al (113)
1997
Year
2000
1998
1999
1999
1999
2001
1998
1998
Patients, n
548
211
750
832
802
395
373
624
492
Patients with isolates, n
403
112
287
547
400
219
192
290
301
Total isolates, n
498
150
342
577
513
275
181
379
346
Haemophilus influenzae
18
14
31
36
36
35
25
18
17
Moraxella catarrhalis
9
7
15
16
12
13
14
21
14
Streptococcus pneumoniae
5
17
25
18
11
3
8
7
6
Staphylococcus aureus
13
13
5
3
9
3
7
20
10
Pseudomonas species
Bacterial isolates, %
NR
15
1
8
NR
3
13
NR
5
Haemophilus parainfluenzae 28
NR
5
2
27
NR
12
6
15
Enterobacteriaceae species
25
5
5
NR
33
19
NR
8
NR
NR Not reported
hypothesis. Finally, there is evidence that there may be antigenic drift in nontypeable H influenzae species so that recurrent infections may actually be by new strains of the bacteria in
some individuals (102,104,105).
Isolation of bacteria during an AECB
Bacteria have been isolated from sputum in up to 60% of
AECB. The most common organism isolated include
H influenzae, H parainfluenzae, S pneumoniae, and M
catarrhalis (Table 1) (99,106-113). Some studies have found
higher numbers of Staphylococcus aureus, Pseudomonas species
and members of the Enterobacteriaceae family. It is not always
clear whether these more virulent organisms are found in
patients with more severe air flow obstruction, more frequent
exacerbations treated with antibiotics, or are due to different
culture techniques. Finding a bacterial pathogen within the
airways of somebody during an AECB does not necessarily
implicate that species as the trigger for the exacerbation. A
number of studies have shown a similar incidence of bacterial isolation from sputum during periods of clinical stability
and AECB (114,115). More recently, investigators have
turned toward the use of bronchoscopy using protected specimen brushes or BAL sampling of the lower airways with subsequent quantitative cultures to determine the importance of
bacteria during episodes of AECB. Four studies have now
been published using these methods and all have shown evidence for significant bacterial infection of the distal airways
in approximately 50% of patients experiencing an AECB
(116-119). Two of these studies were performed in outpatients and demonstrated significant bacterial growth more
frequently in patients during an episode of AECB than at
baseline (117,119). Although many of the bacteria found in
the airways were similar during periods of clinical stability
and exacerbations, the colony counts were significantly elevated during episodes of AECB.
Sputum, bronchial washings and bronchial brushings may
underestimate the presence of bacteria, particularly if the latter have penetrated the epithelial cell layer. Bandi et al (102)
found nontypeable H influenzae in only 26% of bronchial
washings or brushings from clinically stable patients with
chronic bronchitis, and in only 7% of patients with AECB.
However, intracellular nontypeable H influenzae were
demonstrated in bronchial biopsies from 87% of patients
8B
with AECB, 33% of stable patients with chronic bronchitis
and from no healthy controls.
Sethi and colleagues (46) used molecular typing to identify
new strains within a bacterial species in sputum isolates collected
during an AECB. Exacerbations were associated with 33% of visits in which new strains were identified, versus only 15% of visits
in which no new strains were found (P<0.001). These findings
support an important role for bacteria in AECB.
If bacteria are important in inducing exacerbations and contributing to worsening airway inflammation, there should be a
correlation between measures of airway inflammation and sputum culture results during an episode of AECB. Sethi et al (77)
followed a group of COPD patients at regular intervals and cultured either spontaneously expectorated or induced sputum from
individuals who had evidence of an AECB. The sputum specimens were also assayed for IL-8, TNF-alpha and neutrophil elastase, which were used as surrogate markers for neutrophilic
inflammatory responses to acute bacterial infection in the airways. These investigators showed that there were significantly
higher levels of markers of airway inflammation in pathogenpositive exacerbations than in pathogen-negative exacerbations,
supporting a role for these pathogens in AECB.
One of the arguments against the importance of bacteria in
AECB has been that many patients recover without antibiotic
therapy. Up to this point, there have been no characteristic
markers separating a bacterial exacerbation from a nonbacterial
exacerbation, making the study of potential beneficial effects of
antibiotics in AECB very difficult. Anthonisen et al (120)
suggested that antibiotics benefit patients with AECB who
have a triad of increased sputum volume, sputum purulence
and worsening dyspnea. It was only in patients with all three of
these symptoms that antibiotics seemed to have a statistically
significant and clinically relevant advantage over placebo.
Some studies purporting to show no additional benefits of
antibiotics compared with oral corticosteroids alone included
many patients who had underlying asthma, and no effort was
made to document the presence of bacterial infection (121).
More recently, Stockley et al (122) compared the presence of
purulent sputum with the results of bacterial cultures. During
periods of exacerbation, a positive bacterial culture was
obtained from 84% of patients if their sputum was purulent,
whereas positive cultures were obtained in only 38% of
patients with mucoid sputum. In addition, when the patients
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were restudied in a stable state between exacerbations, the
incidence of a positive bacterial culture was similar in both
groups, approximating 40%. Overall, they felt that the presence of purulent sputum was 94.4% sensitive and 77% specific
in predicting the yield of a high bacterial load in culture and in
identifying the group most likely to benefit from antibiotic
therapy. In a follow-up to this study, the same authors correlated the presence of sputum purulence with the levels of certain
inflammatory markers including MPO, IL-8 and LTB4
(123,124).
The role of viruses and atypical organisms, such as
Mycoplasma and Chlamydia species, is becoming clearer. There
are three separate mechanisms whereby these organisms may
have a role in COPD and AECB. First, infection with certain
agents at a young age may make airways more susceptible to the
effects of cigarette smoking and increase the risk of chronic
bronchitis later in life. This has been suggested both with adenoviral infections in childhood (33) and with Chlamydia pneumoniae infection (125). Second, these organisms can cause AECB
in their own right. Up to one-third of AECB are related to viral
or Mycoplasma infections (82,114,126-128). C pneumoniae is
thought to account for only 5% to 10% of acute exacerbations of
COPD (129,130), although one recent study suggested that it
may be involved either alone or as a cofactor in up to 22% of
AECB (131). The third mechanism whereby viruses and atypical organisms may be involved in AECB would be by causing a
primary infection that worsens lower airway inflammation,
which enables a secondary increase in bacterial proliferation
that would then play a role in the exacerbation (131,132).
There is evidence that respiratory virus infections are associated
with more severe and frequent AECB and may contribute to
chronic infection in COPD (128). Rhinovirus infection had
been shown to be involved in precipitating AECB (133) and a
recent study suggests that rhinovirus infection leads to an elevation of lower airway IL-6 levels (134). This worsening of lower
airway inflammation may theoretically enhance bacterial proliferation, leading to secondary bacterial involvement in these
episodes of AECB as well.
AECB
Like the disease itself, exacerbations of chronic bronchitis are
defined clinically. It has become traditional to use some combination of the following three criteria originally described by
Anthonisen and colleagues (120) to define AECB: increased
cough and sputum, sputum purulence and increased dyspnea
over baseline. Unfortunately, there are no characteristic laboratory or radiographic tests to make the diagnosis of AECB, so
the definition of an exacerbation remains problematic.
Seemungal and colleagues (134) have proposed major and
minor criteria to define an exacerbation. The major criteria
are the three proposed by Anthonisen. Minor criteria include
wheezing, sore throat, cough and symptoms of a common cold
such as nasal congestion or discharge. They defined an exacerbation as the presence of at least two major symptoms, or
one major and one minor symptom, for at least two consecutive days. It is clear that the incidence of AECB will vary
depending on which definition is used. Using the Anthonisen
criteria, the typical patient with COPD will average two to
three AECB episodes annually. Other causes of deterioration
include congestive heart failure, pneumonia, pulmonary
emboli, pneumothorax, inappropriate oxygen administration
and drugs such as tranquilizers.
Can Respir J Vol 10 Suppl B July/August 2003
Approximately 50% of exacerbations, particularly those
meeting the Anthonisen criteria, are believed to result from
infection, but exposure to allergens, pollutants or irritants (cigarette smoke, dust) may all precipitate a worsening of chronic
bronchitis. Exacerbation rates are an important determinant of
disease-specific health status as measured by a standard quality
of life questionnaire (135). Exacerbations may lead to hospitalization, which carries with it a 4% short term mortality rate
for patients with mild to moderate disease (136), but as high as
24% if admitted to an intensive care unit with respiratory failure (137-140). This latter group of patients with severe disease
have one-year mortality rates of up to 46% (137-139). Many
patients requiring hospitalization for AECB will require
subsequent readmissions because of persistent symptoms
(137,140,141). In addition, they will experience at least a temporary decrease in their functional abilities (142).
There are no characteristic physical findings in AECB.
Although some authors have suggested that severe exacerbations of chronic bronchitis are associated with a body temperature of higher than 38.5°C (143), this idea is not widely
accepted. In fact, a study of patients hospitalized because of a
severe AECB found that the mean temperature on admission
was 36.4°C (137). The presence of an elevated body temperature should suggest a viral infection (128) or underlying pneumonia as a cause of an AECB. The lack of a clear definition of
AECB has hampered investigation into appropriate therapy of
the disorder.
Chest roentgenograms are not helpful in making the diagnosis of AECB, although they should be considered if there is
a possibility of pneumonia or congestive heart failure contributing to the presentation. An exception to this general rule
should be made for patients seen in emergency rooms or admitted to hospital. In these settings, routine chest roentgenograms
have been shown to reveal abnormalities that lead to changes
in management in 16% to 21% of patients (144-146).
Sputum Gram-stain and culture have a very limited role in
the investigation of the etiology of AECB because, for reasons
discussed above, the airways of patients with chronic bronchitis are chronically colonized with bacteria. Therefore, the finding of a particular organism does not necessarily imply a causal
relationship to the AECB. Sputum analysis should be reserved
for patients with frequent exacerbations or chronic purulent
sputum in whom the presence of more virulent and/or resistant
bacteria is more likely (Level III evidence).
Objective measurements of lung function are necessary to
confirm the presence of air flow obstruction. There is a poor
correlation between chronic symptoms of dyspnea and measurement of FEV1 (147). In addition, there is a very poor correlation between the amount of sputum produced and the degree
of air flow limitation (43,148). However, FEV1 remains the best
predictor of mortality (149) and has been shown to be important in predicting need for admission to the intensive care unit
(150). There is also evidence that FEV1 is highly predictive of
clinical outcomes during AECB (151). Despite this there is
continued evidence that spirometry is being underutilized in
the patient group at risk of developing chronic bronchitis (152154). The continued reliance on clinical indicators as a basis for
obtaining spirometry leads to the underdiagnosis of COPD and
other causes of air flow obstruction. Despite this, strong argument in favor of screening spirometry in high-risk individuals,
there is little evidence to suggest that spirometry has a role in
evaluating an AECB. Measurement of FEV1 may not be possible
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in a patient with a severe AECB. In addition, it is not clear that
there is a correlation between transient falls in lung function
and the severity of the exacerbation as defined by the
Anthonisen criteria (120). Therefore, although it is helpful to
know the premorbid FEV1 as a predictor of adverse outcome
during an AECB, it is not necessary that spirometry be performed during the actual exacerbation (Level III evidence).
However, the development of an AECB should be a motivating
factor to obtain objective measurements of pulmonary function
after recovery in patients who had not previously had spirometry (Level III evidence). The use of peak expiratory flow rates
(PEFR) is not recommended as a substitute for spirometry
because it is much more effort-dependant, has not been demonstrated to predict outcome in COPD and should not show variability in a disease defined as having fixed air flow obstruction.
Management of AECB
Chronic bronchitis is a clinical entity related to chronic/
intermittent mucous hypersecretion. It represents a diagnostic
category within the spectrum of COPD in which chronic air
flow limitation may or may not be present. AECB are by definition associated with increases in the quantity and/or purulence of the sputum, with or without increased dyspnea. The
large body of literature focusing on the treatment of AECB is,
in most cases, focused on antimicrobial therapy.
The phrase ‘exacerbation of COPD’, on the other hand,
typically refers to increases in dyspnea in association with
increases in the degree of air flow limitation, with or without
clinical manifestations of respiratory infection. Increased sputum volume and/or purulence may be present, but are not necessary for the diagnosis of COPD exacerbation.
The problem that becomes apparent in reviewing the
COPD literature is that the majority of studies regarding treatment of exacerbations beyond antibiotics (oxygen, bronchodilators, corticosteroids, etc) are focused on exacerbations
of COPD; hence, results are generally extrapolated, perhaps
inappropriately, to the management of AECB.
Treatment of AECB should provide symptomatic relief,
prevent transient loss of pulmonary function that may lead to
hospitalization and lead to a re-evaluation of the disease in a
particular patient to determine if the risk of future exacerbations can be reduced. Patients should be removed from any
source of irritants that may worsen lower airway inflammation,
including dust, pollutants and first- and second-hand smoke.
Pharmacological therapy aims at decreasing the work of
breathing, reducing airway inflammation, reducing the bacterial burden in the lower airways and treating any accompanying
hypoxemia.
Bronchodilator therapy
Bronchodilator therapy should be employed for the treatment
of dyspnea accompanying an exacerbation. The majority of the
studies examining the role for inhaled bronchodilators in exacerbations of COPD have been done in patients presenting to
the emergency room or hospitalized because of the exacerbation. Therefore, it is not clear whether the results of these studies are applicable to the much larger population of AECB
patients treated at home. In addition, the endpoint most commonly measured is FEV1, and this may not be the most relevant
parameter because it may not change much in a single AECB
episode. Some of the studies comparing anticholinergics to
short-acting beta-agonists have combined asthmatics with
10B
COPD patients. Nonetheless, certain general statements can
be made based on the available literature (155).
Most studies comparing short-acting beta-agonists with
inhaled anticholinergic agents show no appreciable difference
between the two in terms of effects on pulmonary function
(156-159). There may be fewer side effects with ipratropium
than salbutamol (160). Most studies examining the effects of
combination therapy do not report any added benefit of adding
a second agent (156,160-162). One study demonstrated a
greater improvement in FEV1 with combination therapy than
with a beta-agonist alone (163), while another showed shorter
emergency room stays for the group on combination therapy
(164). None of these studies are well standardized in terms of
dose of medication or dosing frequency. Therefore, it is difficult to make specific recommendations. Some patients clearly
benefit from combination bronchodilator therapy and there
does not appear to be a significant increase in side effects with
this combination (Level III evidence). Although there has
been recent interest in the role of long-acting beta-agonists in
the chronic therapy of COPD, these agents have not been
studied in AECB and are not recommended for treatment of
this condition at the present time. A number of studies have
compared the use of metered dose inhalers (MDIs) to nebulized bronchodilators. These studies are occasionally flawed by
using much larger doses of nebulized medications.
Nonetheless, as supported by a meta-analysis of studies in
patients with either asthma or COPD, there does not appear to
be any difference in pulmonary function outcomes between
delivery systems (165). Therefore, the choice of delivery system should be based on cost and the patient’s ability to use
MDIs with a spacer. In most situations, MDIs with an appropriate spacer would be preferred (Level II evidence).
There does not appear to be a role for the initiation of therapy with methylxanthines in AECB. The addition of aminophylline to inhaled bronchodilators has not been shown to
lead to improved FEV1 but does increase frequency of side
effects (166,167). For patients who are already on an oral
methylxanthine product, it is reasonable to continue the medication during an AECB. However, one must keep in mind
possible drug interactions with antibiotics (eg, ciprofloxacin,
clarithromycin) and adjust the dose accordingly (Level III
evidence).
Oxygen therapy
Patients with chronic bronchitis are at risk of developing hypoxemia during an exacerbation. This can lead to hypoxic pulmonary vasoconstriction with subsequent right heart strain and
possible cor pulmonale. In addition, hypoxemia can increase the
risk of myocardial ischemia in the elderly COPD population and
can have neuropsychiatric side effects. Low-flow oxygen should
be administered if hypoxemia is present (168-171). Excess use of
oxygen should be avoided as this may lead to progressive hypercapnia, either by decreasing hypoxic ventilatory drive or by
worsening ventilation-perfusion mismatching within the lung
(172,173). The goal of therapy with supplemental oxygen
should be to maintain a partial pressure of oxygen in arterial gas
at or just above 60 mmHg. Decisions regarding long term need
for supplemental oxygen should not be made during an AECB,
because up to 50% of patients requiring oxygen during an exacerbation will no longer meet the criteria for home use if
reassessed one to three months later (174-176).
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TABLE 2
Randomized trials of corticosteroids in chronic obstructive pulmonary disease exacerbations
Study (Reference)
Year
Emerman et al (190)
1989
Albert et al (371)
1980
Sample size
96
44
Intervention
Outcomes
Methylprednisolone 100 mg × 1 dose
Methylprednisolone
Thompson et al (191)
1996
27
Niewoehner et al (193)
Maltais et al (201)
1999
1999
2002
56
271
199
NS
Admission
NS
<0.001
FEV1 tid x 72 h
Prednisone 30 mg × 3 days,
40 mg × 3 days, 20 mg × 3 days
Davies et al (192)
FEV1 at 3 and 5 h
Pre- and postbronchodilator
0.5 mg/kg q6h × 72 h
P*
Prednisolone 30 mg od × 2 weeks
Methylprednisolone 125 mg q6h × 72 h
Improvement in P02
0.002
Improvement FEV1
0.006
Decreased treatment failures
0.002
FEV1 postbronchodilator
<0.0001
Length of hospitalization
0.027
Treatment failure
0.04
followed by prednisone 60 mg od × 4 days
Length of hospitalization
0.03
tapered over 2 versus 6 weeks
Increased FEV1 days 1-3
<0.05
Prednisolone 30 mg q12h × 3 days
Postbronchodilator FEV1
<0.05 versus placebo
Budesonide 2 mg q6h × 3 days
NS budesonide
versus prednisolone
*Steroids versus placebo. FEV1 Forced expiratory volume in 1 s; NS Not significant; P02 Partial pressure of oxygen
Mucous clearing strategies
Expectorants or cough suppressants are not effective during
exacerbations of chronic bronchitis. Pharmacological therapy
to enhance mucous clearance has not been shown to improve
lung function or hasten the clinical recovery in AECB
(177-179), although it may produce a subjective improvement
(177). There is no beneficial effect of chest physiotherapy on
the time to recover from an AECB (180,181). There is even
some suggestion of worsening pulmonary function and gas
exchange with this form of therapy (182,183). Therefore, we
do not endorse the use of mucolytic agents or chest physiotherapy during AECB (Level II evidence). Patients should be
kept adequately hydrated to prevent excessive mucous viscosity
but increased fluid intake should be avoided except by patients
who are clearly dehydrated (Level II evidence).
Miscellaneous therapies
At this point, there is no evidence supporting the use of
leukotriene receptor antagonists in AECB.
The use of noninvasive ventilation (NIV) in acute exacerbations of COPD has been demonstrated to reduce mortality
and decrease the need for intubation and mechanical ventilation (184,185) (Level I evidence). Overall, NIV also reduces
morbidity and hospital or intensive care unit length of stay
(186). Factors predicting success include good level of consciousness at the start of the trial, higher pH and lower partial
pressure of carbon dioxide in arterial gas (PaCO2), and
improvements in pH and PaCO2 within 1 h of NIV initiation
(187-189). Poor outcomes are associated with decreased
adherence to NIV protocol, presence of pneumonia and poor
nutritional status.
Corticosteroid therapy
Since our first set of guidelines was published in 1994, a number
of randomized, placebo-controlled trials have been published
confirming the value of oral and/or parenteral corticosteroids in
the therapy of AECB. These trials are summarized in Table 2.
These studies demonstrate that systemic steroids lead to a faster
improvement in pre- and postbronchodilator FEV1, more rapid
recovery of partial pressure of oxygen, decreased treatment failures and shorter hospitalization rates. The one study that failed
Can Respir J Vol 10 Suppl B July/August 2003
to show a benefit of parenteral steroids during an exacerbation
of COPD used only a single dose of methylprednisolone 100
mg in the emergency room and measured FEV1 outcomes 1 h
and 3 h following this bolus (190). The follow-up interval may
not have been sufficient to detect a significant improvement
because it is generally felt that steroids take at least 6 h to have
a beneficial effect.
There are a number of limitations to these trials. All but
one study (191) were performed in emergency rooms or hospital wards, so that the results may not be applicable to outpatient populations. The severity of the underlying lung disease
was quite variable, although the majority of patients enrolled
had moderate to severe underlying disease. Finally, the dose
and duration of corticosteroid therapy varied widely among
studies, making it virtually impossible to provide specific treatment recommendations. One must carefully weigh the pros
and cons of higher dose and more prolonged corticosteroid
therapy in this elderly group of individuals. In the studies
quoted, the major side effect in the steroid-treated group was
hyperglycemia (192,193).
Systemic therapy may have additional beneficial effects
aside from speeding up recovery from an AECB. A retrospective study performed in an emergency room setting demonstrated that steroid-treated individuals had a significantly
reduced likelihood of relapse compared with the group not getting steroids (194). Seemungal and colleagues (134) followed a
cohort of 101 COPD outpatients over 2.5 years during which a
total of 504 exacerbations were recorded. It was up to the individual treating physician to choose whether to add steroids to
the treatment plan for any patient. Patients receiving prednisolone had more severe exacerbations as reflected by larger
falls in PEFR and a longer recovery time for symptoms and
PEFR. However, the rate of recovery of PEFR was faster in the
group given prednisolone. Of greater interest, steroids prolonged the time to the next exacerbation from a median of
60 days in the group not receiving prednisolone to 84 days in
the treated group (P=0.037). In contrast, antibiotic therapy
had no effect on recovery time or time to next exacerbation.
The mechanism(s) through which corticosteroids speed up
recovery in AECB remain(s) unclear. Steroids are effective in
terms of reducing airway edema and mucus hypersecretion,
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both of which play a role in the pathogenesis of AECB. Airway
eosinophilia and activation have been demonstrated in some
patients with AECB (79,134) and steroids are very effective at
reducing eosinophil migration into the airways and preventing
degranulation. Steroids are capable of increasing secretory
leukoproteinase inhibitor (SLPI) in airway epithelial cells in
vitro and in airway secretions measured in induced sputum
(195,196). SLPI has antiviral and antibacterial activity (197)
and sputum SLPI levels are lower in COPD patients with more
frequent exacerbations (124). Therefore, their effect on reducing the frequency of exacerbations may be on the basis of both
decreased airway inflammatory effects and decreased risk of
mucosal infections. However, this hypothesis will need to be
tested in the future.
There is good evidence to support the use of oral or parenteral steroids for most patients with moderate to severe
AECB (Level I evidence). The exact dose and duration of
therapy should be individualized and more specific recommendations must await further evidence. It appears that 10 days of
therapy is more effective than three days, but no other comparisons have been made (198). We recommend treatment for
periods of five to 14 days (Level III evidence). Whether
patients with mild disease (FEV1 60% to 70% greater than predicted) also benefit from a course of oral steroids during AECB
is unknown at the present time. There are significant health
consequences to the use of continuous oral corticosteroids in
COPD and similar deleterious effects may occur in patients
treated with frequent short courses (199).
The role for inhaled steroids in AECB has not yet been
defined. Although some studies have failed to demonstrate a
role for inhaled steroids in speeding up symptom resolution in
AECB, these trials have not been designed to answer this question (200). A recently published prospective, randomized trial
comparing high dose nebulized budesonide (2 mg every 6 h for
72 h) versus prednisone (30 mg twice daily for 72 h) demonstrated no difference between active treatments, with both
being superior to placebo in terms of recovery of FEV1 (201).
ANTIBIOTIC THERAPY
Despite many decades of therapeutic trials, the role for antimicrobial therapy in AECB treatment remains controversial.
There are a number of reasons for this. Most comparative
antimicrobial trials demonstrate equivalence (1). These trials
are mainly performed for registration purposes. Accordingly,
they are powered to demonstrate equivalence only as required
by the licensing authorities, and intrinsic superiority such as
improved in vitro activity or excellent pharmacokinetics and/or
pharmacodynamics cannot be demonstrated. Complicated
patients with pretreatment-resistant pathogens or with comorbid conditions that might interfere with the activity or assessment of the antimicrobial agent are usually systematically
excluded. Most clinical studies do not capture subtle outcome
differences between agents such as speed of recovery, microbiological eradication rates and time to next occurrence. As currently designed, these studies demonstrate the efficacy of the
antimicrobial but cannot demonstrate effectiveness (performance in real life circumstances). This part of the document will
emphasize data supporting the use of antibiotics in AECB.
Emerging concepts regarding antimicrobial resistance will be
discussed. Finally, the data to support a simpler risk stratification
scheme will be presented and specific antimicrobial recommendations for each risk category will be offered.
12B
The controversial role of antibiotics has been somewhat
clarified by more recent studies. Randomized, placebocontrolled antimicrobial trials conducted in previous decades
were inconclusive (202-207) (Table 3). Many of the earlier
studies were not powered to reach a definitive conclusion, but
more recent well-designed studies have concluded that antibiotics are effective. Anthonisen and coworkers (120), in a landmark study, developed a classification system to identify
patients likely to be infected with bacterial pathogens based on
presenting clinical symptoms. A type I exacerbation was
defined as a patient presenting with increased dyspnea,
increased sputum volume and sputum purulence. A type II
exacerbation referred to a patient with two of these symptoms,
while a type III exacerbation occurred when a patient had only
one symptom. Patients exhibiting a type I or type II exacerbation had a demonstrable benefit from antimicrobial therapy
(more likely to resolve in 21 days, more rapid recovery of peak
flow, shorter clinical illness, fewer patients exhibiting deterioration after the first 72 h) implying a bacterial etiology, while
those with a type III exacerbation did not differ from patients
receiving placebo. Allegra and coworkers (208), in another
well-designed, randomized trial involving a large number of
patients, demonstrated the superiority of amoxicillin/
clavulanate to placebo. A more recent randomized, doubleblind, placebo-controlled study in 93 mechanically ventilated
patients with an exacerbation demonstrated that the use of fluoroquinolones compared with placebo was associated with a
reduction in mortality, duration of hospital stay and time on
mechanical ventilation, and a decrease in the need for additional antibiotics (209). A conflicting study purporting to
show no benefit of antibiotic therapy is flawed by including
patients with relatively mild disease and/or asthma, with the
latter group undoubtedly improving due to the oral steroids
that the patients were given (121).
Although the Anthonisen classification is helpful in predicting an antimicrobial response, it had only a sensitivity of
59% and a specificity of 60% in predicting a bacterial exacerbation (210). While this is an improvement, this would suggest
that this particular classification system is only moderately successful in predicting a bacterial etiology and confirming the
role of antimicrobials. The presence of green (purulent) secretions in a patient with a history of COPD was 99.4% sensitive
and 77.0% specific for the yield of high bacterial load, and
may identify a clear subset of patients likely to benefit from
antibiotic therapy (122). It should be pointed out that the
patients in this study all had increased dyspnea, so that they
were all at least Anthonisen Type II. In a meta-analysis examining placebo-controlled trials in AECB, antibiotic therapy
improved clinical outcomes and hastened clinical and physiological recovery (211).
Traditionally, older antibiotics such as ampicillin, tetracycline or trimethoprim/sulfamethoxazole (TMP/SMX), have
been the standard treatment choices for AECB. The development of resistance of primary respiratory pathogens to these
antibiotics, the recognition of more virulent Gram-negative
organisms especially among patients with significant impairment of lung function, and the development of more potent,
broad spectrum agents with improved coverage of the major
respiratory pathogens has forced a re-examination of antimicrobial choices.
A failure rate that varies from 13% to 25% can be expected after treatment with traditional first-line antibiotics
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Management of AECB
TABLE 3
Randomized trials of antibiotics in acute exacerbations of chronic bronchitis
Comparators
Placebo versus oxytetracycline
Patients
(n/n)
37/37
Outcome of therapy
Treated patients lost half as much time from work
Reference
Elmes et al, 1957 (202)
and exacerbations were shorter
Placebo versus oxytetracycline
27/26
Treated patients recovered sooner and deteriorated less often
Berry et al, 1960 (203)
Placebo versus ampicillin
28/28
No significant difference in clinical response
Elmes et al, 1965 (204)
10/10/9
No significant differences
Peterson et al, 1967 (205)
86/84/89
Antibiotic therapy superior to placebo but
Pines et al, 1972 (206)
Placebo versus physiotherapy
versus chloramphenicol
Placebo versus chloramphenicol
versus tetracycline
Placebo versus tetracycline
Placebo versus either co-trimoxazole,
no differences between antibiotics
100% versus 100% clinical response
Nicotra et al, 1982 (207)
180/182
20/20
55% versus 68% success (P<0.01)
Anthonisen et al, 1987 (120)
179/190
50.3% versus 86.4% success (P<0.01)
Allegra et al, 1991(208)
Absolute risk reduction of 45.9 in death or need for additional
Nouira et al, 2001(209)
amoxicillin or doxycycline
Placebo versus co-amoxiclav
Placebo versus ofloxacin
47/46
antibiotics in ventilated patients (P<0.0001)
(amoxicillin, TMP/SMX, tetracycline, erythromycin) (212214). This initial treatment failure may be associated with
enormous additional expenditures, especially among patients
with significant compromise of lung function. These patients
may require hospitalization and are at risk for the development
of respiratory failure (214). Resistance to β-lactam antibiotics
such as ampicillin can be expected in 20% to 40% of isolated
strains of H influenzae and in greater than 90% of strains of M
catarrhalis (215,216). There are no clinical features that can
predict the presence of β-lactamase-producing bacteria, except
that patients with these organisms tend to have more courses
of antibiotics (217). Penicillin resistance is now found in
greater than 35% of S pneumoniae isolates in some studies and
is increasing worldwide (218). Penicillin resistance in Canada
has been reported as high as 30% (216). Penicillin resistance is
also a marker for resistance to other classes of antibiotics
including the cephalosporins, macrolides, β-lactam/β-lactamase inhibitors, TMP/SMX and tetracyclines (219). Whereas
antibiotic resistance and widespread clinical failure in lower
respiratory tract infections have not been linked at this time,
this may only be a reflection of the rapidly changing antimicrobial environment. Most ‘resistant’ organisms demonstrate
low levels of penicillin resistance (minimal inhibitory concentration [MIC] of 2 µg/ml or less). Because the doses of
β-lactams usually prescribed achieve high levels in blood,
these levels of resistance may be overcome. If levels of resistance continue to increase, however, the value of many classes
of antibiotics including β-lactams, cephalosporins, macrolides,
tetracyclines and trimethoprim-sulfonomide combinations
may diminish. Antibiotic overprescribing for nonbacterial
infections is a major factor in the emergence of bacterial resistance. Attention must be paid to improving antibiotic use as
well as to identifying those patients who would benefit from
aggressive broad spectrum therapy. One advantage of a risk
stratification system is that patients not requiring antimicrobial therapy can be identified as well as those requiring more
aggressive therapy.
β-Lactam resistance: There are three major mechanisms of
β-lactam resistance: alteration of the antibiotic target sites
(penicillin binding proteins [PBPs]), inactivation of the drug by
enzymes produced by the bacteria (β-lactamases), and reduction of drug permeability into or out of the cell (220). Efflux
Can Respir J Vol 10 Suppl B July/August 2003
and bypassing a blocked pathway do not play a role in this class.
Target modification: Target modification is the only mechanism of resistance of S pneumoniae to β-lactams. Reduced susceptibility of S pneumoniae to the β-lactams has been the result
of the remodelling of the PBPs so that there is decreased binding affinity. Pneumococci for which the MIC of penicillin is
less than 0.1 µg/ml are defined as penicillin-susceptible, those
for which the MIC is 0.1 µg/mL to 1.0 µg/mL are defined as
penicillin-intermediately resistant and those for which the
MIC is greater than 1.0 µg/mL are defined as penicillin-resistant (221) (Table 4). Penicillin-nonsusceptible S pneumoniae
(PNSP) are those that have an MIC of 0.1 µg/mL or greater.
Resistance trends and clinical significance: The prevalence of
PNSP continues to increase worldwide. Rates of resistance
vary from 20% to 80% (216,222-228). Jacobs et al (225) in a
United States surveillance study found that penicillin-resistant
strains were more frequent than intermediately resistant ones
(32.5% versus 18%). Zhanel et al (223) found in a crossCanada surveillance study that penicillin-intermediately
resistant and resistant strains occurred at rates of 14.8% and
6.4%, respectively.
Despite the widespread prevalence of nonsusceptible pneumococci, the clinical impact of using a b-lactam to treat a
patient with a respiratory tract infection due to such a strain is
uncertain (229-231). The S pneumoniae breakpoints for penicillin were established to predict efficacy in infections such as
meningitis, where levels might barely reach the 2 µg/mL level
established for penicillin resistance. In contrast to antibiotic
concentrations in the cerebrospinal fluid (CSF), peak serum
and tissue concentrations of intravenously administered b-lactam antimicrobials may be considerably higher than the MICs
of intermediate or resistant pneumococci. In the setting of
pneumococcal bacteremia and/or pneumonia, current levels
of penicillin resistance have not had any significant impact on
mortality in adults. Pharmacokinetic/pharmacodynamic data
suggests that bacteremic and respiratory tract infections due
to pneumococci will only result in clinical failures when treated with a b-lactam when the penicillin MIC is 4 µg/mL or
higher (230). Less than 2% of pneumococcal isolates have
MICs of 4 µg/mL or higher (Table 4) (232).
The increasing prevalence of penicillin-resistant pneumococci may have a greater impact on the activity of the oral
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TABLE 4
In vitro activities of 16 antimicrobials against 2245 isolates of Streptococcus pneumoniae collected from across Canada
during 2000 (372)
µg/mL)
Minimal inhibitory concentration (µ
Antimicrobial
0.007
0.015
0.03
0.06
0.12
0.25
0.5
1
2
4
8
Penicillin
586*
1233
147
75†
18†
18†
38†
92
38
–
Amoxicillin
84*
1153
734
73
37
46
74
33
10†
1
109†
43
1
1
1824*
Ceftriaxone
60
16
32
64
3‡
41
40
126
Ciprofloxacin
2*
63
892
1188
68†
7
7
6
9
Levofloxacin
1*
19
832
1355
16
2†
5
12
3
1
Gatifloxacin
1*
19
548
1612
40
4
3†
14
3
Moxifloxacin
25*
449
1675
74
1
0
12†
8
1
1
BMS-284756
44*
294
1533
344
9
4
10
6
Gemifloxacin
588*
1214
401
20
3
11
6
1
1
1960*
10
Doxycycline§
Chloramphenicol
1984*
Erythromycin
Clindamycin
91
72
10
2198*
2
45‡
9
3†
10
28
42
28
18
12
24
87‡
3†
0
4
4
2
5
6
13
90‡
–
144
24
0
0
1‡
Telithromycin
59
49
37
23
40
19
2
ABT-773
2102*
49
40
39
12
2
1
–
29
966
1054
94
–
1501*
254
149†
87†
85
Linezolid§
–
–
2118*
2016*
Trimethoprim/sulfamethoxazole
128
*Less than or equal to; †Intermediate category where applicable; ‡Greater than or equal to; §Only 2143 isolates tested
cephalosporins. Oral cephalosporins have a disproportionate
loss of activity against strains of PNSP. Therefore, as penicillin
resistance rates increase, not only do the rates of cephalosporin
resistance increase, but also the degree of resistance increases.
Reports of clinical failures of cephalosporin treatment of pneumococcal infections caused by strains of S pneumoniae highly
resistant to penicillins are rare. However, the numbers of
penicillin-resistant pneumococci causing disease in prospective studies designed to evaluate the impact of resistance have
been small (229).
In January 2002, the NCCLS published new susceptibility
interpretive criteria for cefotaxime and ceftriaxone for nonmeningeal isolates of S pneumoniae (233). Previously susceptibility interpretive breakpoints were less than or equal to
0.5/equal to 1/greater than or equal to 2 µg/mL for
susceptible/intermediate/resistant, respectively. However, these
breakpoints were derived largely from considerations in the
treatement of meningitis. The Subcommittee on Antimicrobial
Susceptibility Testing of NCCLS reviewed surveillance susceptibility data, pharmacokinetic-pharmacodynamic data in animal
models of infection, clinical data and a simulated trial evaluating the probability of attaining target serum levels relative to
various MICs. As a result of this review, the NCCLS has
agreed to publish new interpretive criteria for nonmeningeal
isolates of S pneumoniae. The changes are largely designed to
clarify the efficacy of these drugs in nonmeningeal infections
due to S pneumoniae strains with MICs of 1 µg/mL or less.
Thus, new interpretive criteria for susceptibility of cefotaxime
and ceftriaxone for S pneumoniae in nonmeningitis are less
than or equal to 1/equal to 2/greater than or equal to 4 µg/mL
for susceptible/intermediate/resistant, respectively (233).
Previous interpretive standards for cefuroxime categorized
isolates of pneumococci with a cefuroxime MIC of 2 µg/mL
or greater as resistant (221). However, pharmacokinetic/
pharmacodynamic data based on a dose of cefuroxime of
14B
15mg/kg twice a day suggests that pneumococcal MICs of
4 µg/mL or greater may be required before clinical failures
occur. The most recent NCCLS guidelines categorize isolates
of pneumococci with a cefuroxime MIC of 4 µg/mL or greater
as resistant (233). Using breakpoints, which were the same as
those in the new NCCLS guidelines, Doern et al (216) found
that of the 41% of pneumococci that were PNSP, in a 1997
North American antimicrobial resistance surveillance
program, 61% and 41% were resistant to cefixime and cepodoxime, respectively. As the prevalence of PNSP continues to
increase, we may see an increase in the number of clinical failures associated with oral cephalosporin therapy of pneumococcal respiratory tract infections.
Antimicrobial inactivation
β-lactamase destroys penicillins and cephalosporins by hydrolysis and is the single greatest cause of resistance to these
antimicrobials. β-lactamases account for greater than 99% of
β-lactam resistance in H influenzae and M catarrhalis
(224,234). Among the various β-lactamase enzymes, the
TEM-1 and TEM-2 enzymes, which hydrolyze ampicillin and
amoxicillin, are the enzymes most commonly seen in
H influenzae (235). M catarrhalis produces ROB-1 and ROB-2
enzymes, which also hydrolyze ampicillin and amoxicillin, but
have no effect on cephalosporins (236).
Studies done in the late 1990s have found rates of β-lactamase
positivity in H influenzae between 30% and 40% in North
America and about 20% in Europe (224,225,237-239).
β-lactamase resistance in M catarrhalis rose very rapidly to over
90% in most countries of the world and has remained stable at
that rate (224,225,237-239). Although there are no NCCLS
breakpoints for M catarrhalis, the degree of activity of all the
antimicrobials used to treat AECB, with the exception of amoxicillin, have excellent activity against this pathogen (239).
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Despite the widespread prevalence of β-lactamase-positive
H influenzae and M catarrhalis, the clinical impact of using a
β-lactam such as amoxicillin to treat a patient with AECB due
to such a strain is unknown.
Macrolide resistance
Resistance to the macrolide antibiotics occurs primarily by target site modification and active efflux (240-242). Acquired
macrolide resistance has not been described in H influenzae
and M catarrhalis. H influenzae appears to have inherent resistance to erythromycin. Azithromycin and clarithromycin are
considerably more active (243). Clarithromycin is metabolized
to 14-OH-clarithromycin, which is two to four times more
active than clarithromycin itself; thus, in vitro susceptibility
testing with only the parent drug inaccurately reflects in vivo
sensitivity. Clarithromycin and 14-hydroxy-clarithromycin
have additive effects against 82% of H influenzae isolates and
are synergistic against 8%.
Target site modification: Resistance due to target site modification is mediated by one of a number of erm (erythromycin
resistance methylase) genes that modify the ribosome target
sites by methylation. The ensuing conformational change
results in reduced affinity between the macrolides, clindamycin and streptogramin B antibiotics and the ribosome,
thereby conferring the MLSB phenotype. This accounts for
about 40% of the macrolide resistance in S pneumoniae in
North America (244). In S pneumoniae, the erm gene is usually
constitutive (244,245).
Resistance due to efflux has been described in S pneumoniae
and is encoded for by the mefE gene (246). It confers erythromycin, clarithromycin and azithromycin resistance only
(M phenotype) (242,247-249). Macrolide resistance due to
efflux accounts for up to about 55% of the macrolide resistance
of S pneumoniae (244).
Approximately 2% of pneumococcal isolates displaying
macrolide resistance have both erm and mef genes.
Approximately 1% to 2% of macrolide-resistant isolates have
neither the erm nor the mef gene. A new mechanism of
macrolide resistance has been described with structural
changes that conceivably may become more common in the
future (250).
Resistance trends and clinical significance: In the United
States, resistance rates of pneumococci to the macrolides vary
from 19% to 30% (225,251). In Canada, macrolide resistance
rates have remained below 10% (216,223).
Resistance due to target site modification (RTSM) results
in high levels of resistance to both clindamycin (MICs 8 µg/mL
or greater) and erythromycin (MICs 64 µg/mL or greater).
Strains resistant on the basis of efflux are susceptible to clindamycin (MICs 0.25 µg/mL or less) and typically have erythromycin MICs of 1 to 32 µg/mL (251). This has begged the
question as to whether a patient infected with an efflux-mediated macrolide-resistant strain would more likely be successfully treated with a macrolide than if the infection was due to a
strain that was macrolide-resistant on the basis of RTSM
(251,252). Currently, there are no clinical data to determine
whether the type of macrolide resistance affects the outcome.
Despite widespread macrolide resistance in S pneumoniae,
there has been sparse clinical data to support that this correlates with clinical failure (253). A possible explanation may be
the pharmacokinetic/pharmacodynamic properties of the
macrolides (252). The concentrations of macrolides in the
Can Respir J Vol 10 Suppl B July/August 2003
alveolar macrophages and extracellular lining fluid of the alveolus are several fold higher than the serum concentrations and
the MICs of macrolide-resistant strains (254).
Fluoroquinolone resistance
Fluoroquinolones directly inhibit DNA synthesis. Inhibition
appears to occur by interaction of the drug with complexes
composed of DNA and either of the two target enzymes, DNA
gyrase and topoisomerase IV. These enzymes are structurally
related to each other, both being tetrameric with pairs of two
different subunits. The GyrA and GyrB subunits of DNA
gyrase are respectively homologous with the ParC and ParE
subunits of topoisomerase IV. Both enzymes act by breaking
both strands of DNA segment, passing another segment
through the break, and then resealing the break.
Fluoroquinolones appear to trap the enzyme on DNA during
the topoisomerization.
Target modification: One mechanism of resistance is the alterations in target enzymes, which are generally localized to specific domains of each subunit type, the quinolone resistance
determining region (QRDR). These alterations arise from
spontaneous mutations in the genes encoding the enzyme subunits and, thus, can exist in small numbers (1 in 106 to 1 in
109 cells) in large bacterial populations.
Fluoroquinolone resistance has been associated most frequently with alterations in the gyrA and/or parC genes. In
S pneumoniae, low-level fluoroquinolone resistance to
ciprofloxacin and levofloxacin has been associated with mutations in the QRDR of parC. However, high-level resistance
requires additional mutations in the QRDR of gyrA (255-259).
Decreased accumulation: Acquired fluoroquinolone resistance due to active efflux in S pneumoniae has been shown to be
due to increased levels of expression of efflux pumps mediated
by the pmrA gene (260). Efflux pumps of this type have broad
substrate profiles and mediate resistance including chloramphenicol and hydrophilic quinolones such as ciprofloxacin,
norfloxacin and ofloxacin. The activity of hydrophobic
quinolones such as levofloxacin, gatifloxacin and moxifloxacin
are less affected (260).
Resistance trends and clinical significance: Emergence of
resistance to the fluoroquinolones has already been described
in Canada, Spain, Hong Kong and Ireland. In Canada, Chen
et al (261) found that the prevalence of ciprofloxacin-resistant
pneumococci (MIC 4 µg/mL or greater) increased from 0% in
1993 to 1.7% in 1997 to 1998 (P=0.01).
Reports of fluoroquinolone resistance in H influenzae and
M catarrhalis are rare (262-266). These have occurred in
patients with chronic or recurrent respiratory infections,
which emphasizes the risk of the development of fluoroquinolone resistance in this type of patient.
Despite the marginal activity of ciprofloxacin against
S pneumoniae, clinical failures of ciprofloxacin treatment of
pneumococcal respiratory tract infections are rare (223,269270). This may be explained in part by the fact that fluoroquinolones, including ciprofloxacin, are relatively
concentrated in lung tissue (lung concentrations exceed serum
concentrations by 1.5 to four fold) (271,272). Although there
are no recommended ciprofloxacin susceptibility breakpoints
for pneumococci, pharmacokinetic/pharmacodynamic data
suggest that an isolate with a MIC of 2 µg/mL or greater should
be considered resistant to ciprofloxacin used at a dose of
500 mg twice a day (273,274). Therefore, as resistance emerges
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and the MIC values increase above the MICs of wild type
organisms, therapeutic levels of ciprofloxacin may not be
achievable, even in the lung (275).
Reports of treatment failures in AECB due to ciprofloxacinresistant pneumococci have started to emerge (276).
TMP/SMX resistance
Biosynthesis of several amino acids and purines depends on
the availability of tetrahydrofolic acid (THF). In addition,
THF is a prerequisite cofactor for essential thymidylate synthesis. In contrast to human cells, which use dietary folates,
most bacteria are unable to take up preformed folic acid
derivatives and must synthesize THF. The sulfonamides and
trimethoprim are structural analogues for intermediaries in
THF synthesis.
Resistance to trimethoprim (TMP) and/or sulfamethoxazole (SMX) can be the result of chromosomal mutations or the
acquisition of genetic elements, which bypass the TMP and/or
SMX blockade (277,278). This has been found in S pneumoniae
and H influenzae (279,280). TMP/SMX resistance in pneumococci is now very high. More than 90% of TMP/SMX resistant
isolates are also resistant to penicillin (281). Conversely,
increasing levels of resistance to β-lactams corresponds with
increasing resistance to TMP/SMX. For example, Thornsberry
et al (224) found that 40% of pneumococci that were highly
resistant to penicillin were resistant to TMP/SMX, whereas
only 3% of penicillin-susceptible pneumococci were.
Therefore, overall rates of TMP/SMX resistance will reflect
the prevalence of PNSP.
Thornsberry et al (224) found that 16% of β-lactamasepositive H influenzae were TMP/SMX resistant versus 7% of
β-lactamase-negative isolates. In recent studies from North
America, 10% to 16% of isolates of H influenzae were
TMP/SMX resistant (224,239). As noted previously,
M catarrhalis remains fully susceptible to TMP/SMX (226,241).
There are no clinical data to show that TMP/SMX resistance
is associated with clinical failures.
Tetracycline resistance
The tetracycline group of antibiotics are either naturally occurring (tetracycline) or semisynthetic (doxycycline, minocycline)
products. The bacteriostatic activity of tetracycline is associated
with reversible inhibition of protein synthesis.
In both Gram-negative and Gram-positive bacteria, efflux
of tetracycline is an important cause of high-level resistance.
All efflux pumps confer resistance to tetracycline but not to
minocycline (minocycline is much more hydrophobic than
tetracycline).
A cytoplasmic protein produced by the resistant organism
interacts or associates with the ribosome, making it insensitive
to tetracycline inhibition (282). These ribosomal protection
proteins, which are encoded by tetM, O, P, Q, and S, protect
the ribosome from the action of tetracycline, doxycycline and
minocycline. Ribosomal protection is the only mechanism of
tetracycline resistance found in S pneumoniae (283).
Thornsberry et al (224) found that 51% of penicillin-highly resistant pneumococci were resistant to tetracycline, whereas only 4% of penicillin-susceptible pneumococci were. In
Canada, approximately 10% of pneumococci are tetracycline
resistant, whereas in the United States, 17% are resistant
(223,224). Tetracycline resistance rates for both H influenzae
and M catarrhalis are less than 1%.
16B
There have been no clinical studies that have addressed
the issue of the impact of tetracycline resistance on clinical
outcome.
Conclusion
Despite the increasing prevalence of resistance in the most
common respiratory pathogens responsible for AECB, there is
very little published clinical information, showing that in vitro
susceptibility results predict clinical outcome. This may be in
part due to the fact that clinical trials carried out for registration purposes are designed to show equivalency and do not
include patients that are infected with a pathogen that is
resistant to the study drug. In addition, it is only recently that
the prevalence and degree of resistance have increased dramatically. As the prevalence of more highly resistant strains
increases, we are now seeing cases of clinical treatment failures
(276) and we suspect that these will increase in frequency.
RISK FACTORS FOR TREATMENT FAILURE
Published failure and relapse rates for AECB in the literature
vary from 17% to 32% depending on the definition used
(Table 5). Identification of patients at risk of failing standard
antimicrobial therapy with the usual first-line agents might lead
to improved antimicrobial prescribing. Ball et al (212) enrolled
471 patients with AECB characterized by increased dyspnea,
sputum volume and purulence. The median number of AECBs
in the previous year was three, and one-third of the patients had
cardiopulmonary disease (ischemic heart disease with/without
cor pulmonale). Clinical features at presentation and antibiotic
therapy did not predict recovery. However, an increased number of chest infections in the previous year and coexistent cardiopulmonary disease were predictors for returning to the
physician with a chest problem. Patients with more than four
treated exacerbations in the previous year were 2.11 times more
likely to fail initial management than patients without this risk
factor. The presence of coexistent cardiopulmonary disease
increased the odds of failure by 2.3 times. The presence of cardiovascular comorbidity and more than four exacerbations in
the previous year had a sensitivity of 75% and specificity of
47% in predicting return to the prescribing physician for further
treatment.
In a retrospective study, Dewan and colleagues (284)
reviewed the clinical experience with 107 patients in a
University Veterans Administration clinic over a 24-month
observation period. They observed a 14.7% failure rate within
four weeks of observation among COPD patients mainly treated with first line antibiotics. More than one-half of the patients
with exacerbations who failed initial treatment required hospitalization. Independent host factors that were associated with
treatment failure included severe impairment of lung function,
use of home oxygen, frequent exacerbations, history of previous
pneumonia and use of maintenance corticosteroids. Using a
stepwise logistic regression analysis, the necessity for home oxygen and frequent exacerbations correctly classified failures in
83% of the patients. In this study, age, the presence of comorbidity, and the choice of antibiotics did not affect treatment
outcome.
In another restrospective study, Miravitlles and colleagues
(285) identified risk factors for relapse after ambulatory therapy
of AECB. Baseline characteristics of coexisting ischemic heart
disease, degree of dyspnea and frequency of visits to the family
physician for respiratory problems in the past year were strongly
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Management of AECB
related to risk of relapse. The severity of AECB, as measured by
the Anthonisen criteria, was not a risk factor for relapse. It
appears that the Anthonisen criteria help to predict outcome in
placebo-controlled trials (120) but not in trials where the
majority of patients are given antibiotics (212,284-286).
TABLE 5
Risk factors for treatment failure
Risk factor
Reference
Frequency of exacerbations
Ball et al, 1995 (212)
Dewan et al, 2000 (284)
Seemungal et al, 1998 (135)
RISK FACTORS FOR HOSPITALIZATION
Patients are admitted to hospital following an inadequate
response to outpatient management, an inability to perform
the activities of daily living due to increased dyspnea or the
development of respiratory failure, often in association with
comorbidities or inadequate home care resources. Knowledge
of risk factors for hospitalization might allow interventions to
prevent this and other unfortunate outcomes (Table 6).
Ball and colleagues (212) demonstrated that the presence
of significant ischemic heart disease or cor pulmonale was the
only predictor of referral to hospital for further management
of AECB. Patients suffering from chronic bronchitis for a
greater number of years were less likely to be referred to hospital. This is in contrast to the findings of Grossman et al
(287), who determined that severity of underlying COPD
(using FEV1 criteria) and duration of disease were the best
predictors of hospitalization. Patients with severe chronic
bronchitis were more than four times more likely to be admitted to hospital than patients with mild to moderate disease
and the risk was similar for patients with disease for more than
10 years. If both risk factors were present, the risk of hospitalization increased almost 20-fold. Kessler et al (288) identified
low body mass, a limited six-minute walk test, significant gas
exchange impairment and pulmonary hemodynamic worsening as predictors of hospitalization. Multivariate analysis indicated that carbon dioxide retention (PaCO2 higher than
44 mmHg) and pulmonary hypertension (mean pulmonary
artery pressure at rest higher than 20 mmHg) were the best
predictors of hospitalization. Age, comorbidity and smoking
habit were not predictive of hospitalization. Vestbo and colleagues (52) demonstrated in the Copenhagen City Heart
Study that chronic mucous hypersecretion was associated
with an excess decline in FEV1 and an increased risk of subsequent hospitalization because of COPD. This relationship
continued to be significant even after adjusting for age, smoking and FEV1. Garcia-Aymerich and colleagues (289) found
that after adjusting for a wide range of potential risk factors,
only three or more admissions in the previous year, lower
FEV1 and underprescription of long term oxygen therapy were
independently associated with a higher risk of admission for
COPD exacerbation.
Miravitlles and colleagues (290) found that the presence of
ischemic heart disease, frequent exacerbations, chronic
mucous hypersecretion, severe impairment of lung function
and advanced age were all risk factors for hospitalization.
Antonelli-Incalzi et al (291) found that the presence of comorbidities and advanced age increased the risk of mortality during
an exacerbation.
RISK STRATIFICATION
A group of high-risk patients in whom the cost of clinical
treatment failure is high may be identified by simple clinical
criteria. Patients with significant cardiac disease, frequent
purulent exacerbations of COPD, generalized debility, malnutrition, chronic corticosteroid administration, use of supplemental oxygen, long duration of COPD, chronic mucous
Can Respir J Vol 10 Suppl B July/August 2003
Miravitlles et al, 2001 (285)
Severity of FEV1 impairment
Dewan et al, 2000 (284)
Ischemic heart disease/congestive
Ball et al, 1995 (212)
Miravitlles et al, 2000 (290)
heart failure
Miravitlles et al, 2001 (285)
Adams et al, 2000 (286)
Increasing age
Antonelli-Incalzi et al, 1997 (291)
Maintenance steroids
Dewan et al, 2000 (284)
Miravitlles et al, 1999 (100)
Use of home oxygen
Dewan et al, 2000 (284)
Chronic mucous hypersecretion
Miravitlles et al, 2000 (290)
FEV1 Forced expiratory volume in 1 s
hypersecretion and severe underlying lung function abnormalities tend to fail therapy with usual antimicrobial therapy and
have early relapse or hospitalization. These patients may be
infected with difficult-to-treat organisms such as Klebsiella
pneumoniae or P aeruginosa, particularly in the presence of
severe impairment of lung function (99). Frequent exacerbations, chronic use of oral steroids and poor underlying lung
function increase the risk for pseudomonas infection
(99,100,118). Frequent courses of antibiotics increase the risk
of infection with β-lactamase-producing bacteria (217).
Treatment directed toward resistant pathogens with potent
antimicrobial drugs might lead to improved clinical outcomes
and overall lower costs, particularly if hospital admissions and
respiratory failure can be prevented. Therapeutic failure leads
to increased cost of care due to extra physician visits, further
diagnostic tests and repeated courses of antibiotics. It may also
lead to more hospitalization and prolonged absence from work.
This greatly increases the cost of AECB treatment (292,293).
Stratification of patients into risk categories may allow the
physician to select targeted antimicrobial therapy to prevent
some of these consequences.
Our proposed, simplified classification system divides
patients into four groups (Table 7). It is important to point out
that this stratification scheme has not been prospectively validated and represents a consensus from our group based on the
evidence available (Level III evidence).
Group 0 patients present with the acute onset of cough
associated with sputum production often in association with a
preceding coryzal illness and fever. While smokers may be
included in this group, these patients have no underlying lung
disease and do not meet the definition for chronic bronchitis.
These patients have acute tracheobronchitis that is usually
viral in origin. The presence of purulent sputum in this previously healthy group of patients is not predictive of a bacterial
infection, unlike the evidence in patients with chronic bronchitis. Because there is no underlying lung disease in this
group, the illness is usually self-limited and runs a benign
course. Most placebo-controlled trials have failed to support a
role for antibiotic therapy in this group of patients, although
meta-analyses of these trials gave conflicting results (294-296).
However, none of these meta-analyses demonstrated a positive impact of antibiotics on duration of illness, limitation of
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TABLE 6
Risk factors for hospitalization
Reference
Ball et al, 1995 (212)
Kessler et al, 1999 (288)
Variable
Vestbo et al, 1996 (52)
Miravitlles et al, 2000 (290)
Garcia-Aymerich et al, 2001 (289)
Confidence interval (95%)
Cardiopulmonary disease
8.89
PaCO2 > 44 mmHg
2.1
1.4–3.1
2
1.3–3.1
Duration of disease
4.6
1.6–13.0
Severity of disease
4.3
0.8–24.6
Duration and severity of disease
19.8
3.2–120.8
1.3–4.5
Ppa > 18 mmHg
Grossman et al, 1998 (287)
Odds ratio
1.73–45.6
Mucous hypersecretion (men)
2.4
Mucous hypersecretion (women)
2.6
1.2–5.3
Ischemic heart disease
1.97
1.25–3.14
FEV1 (% predicted)
COPD admissions > 3 /past year
FEV1 (% predicted)
Underprescription of long term oxygen
0.72 for each 10% drop
0.58–0.888
6.21
1.60–24.07
0.96 (per percentual unit)
0.93–0.98
22.64
2.31–221.88
COPD Chronic obstructive pulmonary disease; FEV1 Forced expiratory volume in 1 s; PaCO2 Partial pressure of carbon dioxide in arterial gas;
Ppa Pulmonary arterial pressure
activities or return to work. Therefore, the routine use of
antibiotics in patients with uncomplicated acute tracheobronchitis is not justified (297). Antibiotic overprescribing for trivial illnesses is a major factor in the emergence of bacterial
resistance. Therefore, efforts at decreasing the use of antibiotics
in group 0 patients may have a positive societal effect. Giving
patients a written leaflet explaining why they do not require an
antibiotic has been shown to reduce use of antibiotics (298).
Patients in group 0 might benefit from one to weeks of inhaled
beta-agonist bronchodilator therapy to reduce the severity and
duration of cough, particularly if wheezing is heard on physical
examination (297).
A small number of patients have a more protracted course.
Mycoplasma pneumoniae and C pneumoniae are known etiologic
agents for acute tracheobronchitis and may be responsible for
those patients not demonstrating a rapid clinical improvement. Treatment with a macrolide or doxycycline might be
considered for patients in whom the cough does not improve
after 10 to 14 days (Level III evidence). There is no evidence
supporting a positive response to this therapy even in the presence of documented infection with an atypical organism. Up
to 20% of adults with a cough lasting more then three weeks
have serological evidence of pertussis. Unfortunately, there are
no clinical features that predict infection aside from exposure
to someone with documented pertussis.
Group I patients have chronic bronchitis defined as having chronic cough and sputum production for at least three
months for two consecutive years. During an exacerbation of
this illness, they demonstrate worsening cough and
increased production of purulent sputum. However, in general, they have only mild to moderate impairment of lung
function (FEV1 greater than 50% predicted value), have less
than four exacerbations per year and have no significant cardiac disease. In this group of patients, the usual pathogens
including H influenzae, S pneumoniae and M catarrhalis are present, although viral infection often precedes bacterial superinfection. Antibiotics have been demonstrated to shorten the
clinical illness. Treatment with virtually any antibiotic is usually successful and the prognosis is excellent. Despite the presence of resistance to β-lactams, outcomes, in general, are
acceptable. Until a prospective pharmacoeconomic or clinical
study demonstrates some advantage for more potent agents
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among this group of patients, the recommendation for simple
therapy such as an aminopenicillin, doxycycline or TMP/SMX
is justified. However, the majority of studies showing beneficial
results from the use of these agents were performed more than
10 years ago, before current concerns regarding emerging
antimicrobial resistance. Given current knowledge about
increasing S pneumoniae and H influenzae resistance to these
older agents, therapy with selected second- or third-generation
cephalosporins or a second-generation macrolide may be
preferable (Level III evidence).
In the face of a treatment failure, alternative therapies such
as a β-lactam/β-lactamase inhibitor or fluoroquinolones can be
used. However, there is no data demonstrating that these failures
are due to resistant organisms or even due to antibiotic failure.
Group II patients have risk factors for treatment failure
such as poor underlying lung function (FEV1 less than 50%
predicted). Alternatively, they may demonstrate only moderate impairment of lung function (FEV1 between 50% and
65% predicted) but have significant comorbidity (ischemic
heart disease, congestive heart failure) and/or experience four
or more exacerbations per year. H influenzae, S pneumoniae
and M catarrhalis continue to be the predominant organisms.
Several studies have indicated that, with declining lung function, enteric Gram-negative organisms may be isolated from
pulmonary secretions. Treatment with medications directed
at resistant organisms, such as a fluoroquinolone or amoxicillin-clavulanic acid should perform better than amoxicillin
or other traditional first-line agents. In addition, there is
increasing evidence suggesting that the enhanced bacterial
eradication associated with fluoroquinolones leads to faster
symptom resolution and results in more prolonged diseasefree intervals compared to cephalosporins and extended spectrum macrolides (Level II evidence) (vide infra).
It is unclear how group II patients who fail to respond to
antimicrobial therapy or who quickly relapse should be treated. Again, it is unclear as to whether failures are due to
antimicrobial failure or some other factor. It makes sense to
treat therapeutic failures or recurrences within three months
of antibiotic therapy with another class of antibiotic, but this
has never been studied. A significant number of patients with
an FEV1 less than 50% predicted are infected with
Pseudomonas species (99,100,118). Whether this occurs only
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TABLE 7
Risk classification and suggested antimicrobial therapy
Group Basic clinical state
Symptoms and risk factors
Probable pathogens
0
Cough and sputum without
Usually viral
Acute tracheobronchitis
None unless symptoms
previous pulmonary disease
I
Chronic bronchitis
Increased cough and
First choice
Haemophilus influenzae,
Alternatives
for treatment failure
Macrolide
persist for > 10 to 14 days
or tetracycline
Second-generation macrolide,
Fluoroquinolone,
without risk factors
sputum, sputum purulence
Haemophilus spp,
second- or third-generation
β-lactam/β-lactamase
(simple)
and increased dyspnea
Moraxella catarrhalis,
cephalosporin, amoxicillin,
inhibitor
Streptococcus pneumoniae
doxycycline, trimethoprim/
sulfamethoxazole
II
Chronic bronchitis
with risk factors
(complicated)
As in group I plus
(at least one of):
As in group I plus
Klebsiella spp + other
FEV1 < 50% predicted
Gram-negatives
> 4 exacerbations/year
Increased probability
Cardiac disease
Fluoroquinolone, β-lactam/
β-lactamase inhibitor
May require
parenteral therapy
Consider referral
of β-lactam resistance
to a specialist
Use of home oxygen
or hospital
Chronic oral steroid use
Antibiotic use in the
past 3 months
III
Chronic suppurative
bronchitis
As in group II with constant
purulent sputum;
As in group II plus
Pseudomonas aeruginosa
Ambulatory patients:
Tailor treatment to airway pathogen
Some have bronchiectasis
and multi-resistant
P aeruginosa common
FEV1, usually
Enterobacteriaceae
(ciprofloxacin)
< 35% predicted, or
Multiple risk factors
(eg, frequent exacerbations
Hospitalized patients:
Parenteral therapy usually
required.
and FEV1 < 50%)
FEV1 Forced expiratory volume in 1 s
in the subset of patients with frequent exacerbations remains
to be clarified. It is reasonable to get sputum samples, if possible, from these patients with multiple risk factors to help guide
subsequent treatment.
Group III patients suffer from chronic bronchial infection
with daily production of purulent secretions. They are subject to
frequent exacerbations characterized by increased sputum production, increased sputum purulence, cough and worsening dyspnea often accompanied by hemoptysis. Some of these patients
have bronchiectasis on high resolution computed tomography
scanning. In addition to the usual respiratory organisms, other
Gram-negative organisms including Enterobacteriaceae and
Pseudomonas species should be considered as potential
pathogens, particularly in patients treated chronically with oral
steroids. Ciprofloxacin is the oral agent with the most activity
against these species and should be considered the agent of
choice when they are identified. As discussed in the previous
paragraph, there is some overlap between patients in group II,
with multiple risk factors, and those in group III.
CLINICAL STUDIES
The next section will summarize clinical studies demonstrating
the efficacy of different classes of antimicrobial agents. The
approach used will review studies with various study designs to
develop definitive recommendations for antimicrobial therapy.
Modelling studies
Backhouse et al (299) used a decision analytic model, comparing amoxicillin, amoxicillin/clavulanic acid, ciprofloxacin and
cefaclor, to determine the most cost effective therapy in highrisk patients with AECB. They concluded that the cheapest
Can Respir J Vol 10 Suppl B July/August 2003
product is not always the most cost effective, and in their study,
found amoxicillin/clavulanic acid to be the most cost effective.
Clinical opinion was used to provide essential data regarding
antimicrobial efficacy rates. They called for prospective clinical trials to reach a definitive answer.
Wool et al (300) compared four antibiotics –
amoxicillin/clavulanic acid, ciprofloxacin, clarithromycin
and rufloxacin – in the management of AECB. They
reviewed 19 published studies to calculate pathogen eradication rates and used Italian costing data to estimate overall
costs. They concluded that amoxicillin/clavulanic acid had
the lowest drug acquisition cost and rufloxacin had the highest efficacy rate. Less cost effectiveness was calculated for
ciprofloxacin and clarithromycin.
In a similar decision analytic model, van Barlingen et al
(301) compared macrolides, fluoroquinolones, penicillins and
cephalosporins in the outpatient treatment of AECB. The key
cost drivers were the clinical success and failure rates of firstline treatment and the cost of hospitalization. They divided
their theoretical patient population into two groups – those
with mild to moderate AECB and those with more severe disease. For patients with less severe disease, they concluded that
the differences among the antibiotic classes were not great but
slightly favoured the macrolides and fluoroquinolones. For
patients with more severe AECB, they concluded that the fluoroquinolones were the most cost effective. The experts selected to adjudicate clinical success rates for the various classes of
antibiotics did not include the penicillins as appropriate therapy
for patients with a severe AECB.
Pechere and Lacey (302) reviewed 12 studies of patients
with AECB and demonstrated a strong correlation (r=0.91)
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between eradication failure rates and clinical failure rates
following treatment with macrolides, penicillins,
cephalosporins, TMP/SMX or fluoroquinolones.
These studies concluded that the antibiotic class with the
lowest acquisition cost was not necessarily the most cost
effective. First-line clinical success rate is the most important
factor in reducing overall costs. The studies reached different
conclusions regarding which class of antimicrobial was the
most cost effective because of the different assumptions used
to create the models.
Database analysis
LeLorier and Derderian (303) examined the role of
ciprofloxacin in the treatment of serious lower respiratory
tract infections. Following the introduction of ciprofloxacin
in the province of Quebec, they noted a decrease in the rate of
hospitalizations for asthmatic bronchitis. This association was
not found in the province of Saskatchewan, where
ciprofloxacin usage was severely restricted. There was a statistically significant correlation between increased ciprofloxacin
prescriptions and the differences between predicted and
observed hospitalization rates. However, ecological correlations are poor models to establish cause-effect relationships,
so these results must be viewed with caution.
Adams et al (286) demonstrated that patients severe
enough to present to an emergency department and subsequently treated with ampicillin had higher recurrence rates of
COPD exacerbations than patients who received other
antimicrobial therapies. The recurrence rate with ampicillin
was 54%, but was 13% if the patient received any other
antibiotic from among choices that included cephalosporins,
TMP/SMX, second-generation macrolides, ciprofloxacin or
amoxicillin/ clavulanic acid (P<0.001). This would suggest
that high-risk patients (presumably anyone requiring emergency department treatment for an AECB) benefit from
aggressive therapy directed at resistant pathogens.
A retrospective study by Destache and colleagues (214)
demonstrated that the use of newer antibiotics, when compared with the usual first-line antibiotics in the treatment of
AECB, reduced both the hospitalization rate and the failure
rate. While the acquisition cost of the newer antibiotics
(cephalosporins, macrolides and fluoroquinolones) was higher, the overall costs of the treated patients given these drugs
were lower. In particular, the group receiving
amoxicillin/clavulanate, azithromycin or ciprofloxacin had
the lowest hospitalization rate, lowest clinical failure rate and
lowest costs compared with cephalosporins or first line therapy.
A recent population-based, retrospective cohort study was
done in Ontario to determine the association between outpatient use of an oral antibiotic and 30-day all-cause mortality
(304). In patients over 65 years of age hospitalized for COPD,
the use of an antibiotic was associated with a significant
reduction in short term mortality.
The previously discussed study by Adams and colleagues
(286) also revealed a significant reduction in relapse rates for
patients treated in the emergency room for AECB with antibiotics when compared with those not receiving antibiotics.
This beneficial effect of antibiotics was not seen with amoxicillin.
In a retrospective analysis of their study that demonstrated
a beneficial effect of amoxicillin/clavulanate versus placebo in
AECB, Allegra and colleagues (305) demonstrated that
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patients with the greatest impairment in lung function and/or
more frequent exacerbations benefited the most from antibiotic
therapy.
Prospective randomized trials
The hypothesis that aggressive antibiotic therapy should be
offered to high-risk patients was tested in a recent, prospective
health economic study. Patients with at least three treated
exacerbations in the past year were randomly assigned to
receive either ciprofloxacin or any nonquinolone-based therapy for their next AECB (306). Clinical endpoints (days of illness, hospitalizations, time to next exacerbation) were blended
with quality-of-life measurements (Nottingham Health
Profile, St George’s Hospital Respiratory Questionnaire,
Health Utility Index) and total respiratory costs from a societal perspective. While the overall results indicated no preference for either treatment arm, in patients with multiple risk
factors (severe underlying lung disease, more than four exacerbations/year, duration of bronchitis greater than 10 years, elderly, significant comorbid illness), the use of ciprofloxacin led
to improved clinical outcome, higher quality of life and less
costs. However, due to the smaller number of patients in this
post hoc analysis, this improvement did not reach statistical
significance.
In a series of double-blind crossover studies, Chodosh (309)
determined that ampicillin 0.5 g to 1 g four times daily was associated with a low failure rate and an infection-free interval
ranging from 117 to 302 days. These studies were conducted in
the 1970s when there was no β-lactamase-producing
H influenzae or M catarrhalis. Ciprofloxacin 750 mg twice daily
gave comparable results. Tetracyclines, TMP/SMX and especially cefaclor were associated with higher failure rates and a
shorter infection-free interval. Two recently published studies
compared ciprofloxacin 500 mg twice daily with clarithromycin
500 mg twice daily and cefuroxime axetil 500 mg twice daily in
group II patients (307,308). These studies demonstrated similar
clinical outcomes but ciprofloxacin had superior bacterial eradication rates. In addition, the time to the next exacerbation was
shortest for clarithromycin (a poor outcome), although this did
not reach statistical significance. A number of other studies
have consistently demonstrated significantly superior bacterial
eradication rates with fluoroquinolones compared to cefuroxime or clarithromycin (107-109).
In the recently completed GLOBE (Gemifloxacin Longterm Outcomes in Chronic Bronchitis) trial (309), gemifloxacin 320 mg once daily for five days was compared with
clarithromycin 500 mg twice daily for seven days. While
short term clinical outcomes were similar, gemifloxacin had a
significantly better bacteriological eradication rate and
demonstrated faster eradication of H influenzae.
Gemifloxacin was superior to clarithromycin in preventing
further exacerbations (71.0% versus 58.5% for no further
exacerbations, P=0.016) and reduced the number of patients
hospitalized for respiratory tract infection over the next six
months of follow-up (0.023% versus 0.0625%, P=0.059).
This is the first well-designed clinical trial to demonstrate
clinical superiority of a more potent antimicrobial on clinically relevant outcomes. In a more recent study comparing
moxifloxacin with amoxicillin, clarithromycin or cefuroxime, use of the fluoroquinolone resulted in higher clinical
and bacteriological success rates and a subsequent reduced
need for additional antibiotics (310).
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Management of AECB
Despite this preliminary evidence that fluoroquinolones
may be a superior choice in terms of bacterial eradication and
delaying time to next relapse, there is not enough evidence to
warrant their use in all cases of AECB. One must carefully balance the potential benefits of these powerful antibiotics with
the risk of developing resistance. There is recent evidence to
suggest that frequent use of fluoroquinolones leads to the emergence of resistant strains and that COPD patients are a major
reservoir for these resistant organisms (311).
SUMMARY OF EVIDENCE REGARDING
ANTIBIOTIC THERAPY FOR AECB
1. Antimicrobial therapy is warranted for patients with
an AECB if they fall into the Anthonisen type I or
type II categories (Level I evidence, two randomized,
large scale double-blind trials, one meta-analysis).
2. Antimicrobial therapy is not warranted for patients
with a type III exacerbation (Level I evidence).
3. Patients can be stratified according to their risk of
treatment failure (Level III evidence).
4. A high-risk group of patients can be identified on
clinical grounds, and the major clinical features are
significant impairment of lung function (FEV1 50% or
lower than predicted), frequent exacerbations (four or
more per year), long duration of disease, significant
comorbidity, use of supplemental oxygen and chronic
oral corticosteroid use (Level II evidence).
5. Risk group 0 patients (acute tracheobronchitis) should
not be treated with antibiotics unless symptoms persist
beyond 10 to 14 days (Level I evidence).
6. For risk group 0 patients with persistent symptoms, a
macrolide or tetracycline is recommended since
M pneumoniae, C pneumoniae, or Bordetella pertussis
may be pathogens (Level III evidence).
7. Although resistant H influenzae and M catarrhalis may
be pathogens, traditional ‘first-line’ agents
(aminopenicillins, doxycycline, TMP/SMX) continue
to be efficacious and are recommended for patients
without risk factors for treatment failure (Level II
evidence). Second-generation macrolides and some
second- and third- generation cephalosporins
(cefuroxime, cefprozil, cefixime) may be better choices
given concerns regarding emerging antimicrobial
resistance (Level III evidence).
8. There are no data to demonstrate that, among group I
patients (low risk for treatment failure), there is any
clinical or economic benefit derived from using more
potent, broader spectrum agents (Level I evidence).
9. Broad spectrum potent agents such as fluoroquinolones
or amoxicillin/clavulanate are recommended for group
II patients (Level III evidence).
Can Respir J Vol 10 Suppl B July/August 2003
10. There is some evidence that fluoroquinolones
perform better than other agents for group II patients
(Level II evidence).
11. Group III patients at risk for P aeruginosa infection
(frequent antimicrobials, structural lung damage and
chronic corticosteroids) should be treated with an
anti-pseudomonal agent (ciprofloxacin). Alternative
agents currently must be given parenterally (Level III
evidence).
12. Patients presenting with a relapse or recurrence of
AECB, within three months of previous antibiotic
therapy, should be treated with a different class of
antibiotics (Level III evidence).
PREVENTION OF AECB
Cigarette smoking remains the primary risk factor for the
development of chronic bronchitis. Although only 15% of
smokers will develop air flow obstruction, more than one-half
will develop chronic cough and sputum production with subsequent increased risk for bacterial colonization and recurrent
episodes of AECB. Unfortunately, in 1999, there were slightly
more than six million smokers in Canada, representing 25% of
the population age 15 years and older (312). Any intervention
that slows the rate of decline in FEV1 is likely to have a major
impact on survival in patients with chronic bronchitis.
Smoking cessation has clearly been shown to reduce the rate of
decline of FEV1 (313). The benefits in terms of decline of lung
function are seen even in those over the age of 60 years (314).
In addition, cessation of smoking has been shown to confer a
survival advantage (Level II evidence) (315). Smoking cessation leads to dramatic symptomatic benefits for patients with
chronic bronchitis (Level III evidence). Coughing stops in as
many as 77% of patients who quit smoking and improves in
another 17%. When coughing stops, it does so within four
weeks in 54% of patients (316). Evidence is lacking that this
decrease in cough and sputum production will lead to a subsequent decline in the frequency of AECB. It is known that
patients with chronic cough and sputum production have
increased numbers of AECB episodes compared to similarly
matched smoking control patients so the hope is that smoking
cessation will lead to fewer exacerbations. Nonetheless, this
enthusiasm must be tempered by the fact that there is evidence
for ongoing airway inflammation even in patients with COPD
who do not currently smoke (317,318). A recent analysis of
patients in the Lung Health Study (56) revealed that recurrent
lower respiratory infections hastened the decline in FEV1 in
current smokers but not in ex-smokers.
A detailed discussion of smoking cessation can be found
elsewhere (319). No single technique to encourage smoking
cessation is successful in all groups of patients; however, recent
studies using a combination of behavioural counselling, nicotine replacement and pharmacological therapy to decrease the
desire to smoke revealed one-year abstinence rates of as high as
35.5% (320). A discussion of smoking behaviour and the setting of a specific cessation date should be part of every physician-patient encounter (Level III evidence).
Patients with chronic lung disease have a higher risk for
complications from influenza infection. By virtue of its ability
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to further damage airway epithelial cells, influenza infection
can lead to secondary bacterial proliferation and an increase in
the frequency of AECB. Serological evidence of influenza A or
B infection has been found in up to 28% of patients with
AECB (126,321,322). In addition, COPD patients infected
with influenza have a significant risk of requiring hospitalization (323). Perhaps this is related to the transient decline in
pulmonary function caused by influenza in a group of patients
with less pulmonary reserve (127). Annual influenza vaccination reduces morbidity and mortality of influenza in the elderly
by 50%. In addition, it reduced the incidence of hospitalization for acute and chronic respiratory conditions by as much as
39% (324,325). Therefore, the use of an annual influenza vaccine for all patients with chronic bronchitis is strongly recommended (Level II evidence). The role for either oral or inhaled
neuraminidase inhibitors, which are effective against strains of
both influenza A and B, are currently being studied in terms of
preventing AECB during influenza outbreaks in high-risk
patients. Therefore, no current evidence-based recommendations can be made. However, high-risk patients who have not
been vaccinated should receive prophylaxis during an outbreak
(Level III evidence).
The value of pneumococcal vaccination in patients with
chronic bronchitis is less well established. At least two metaanalyses looking at efficacy of a 17-valent or less vaccine
resulted in opposite conclusions (326,327). Since 1983, a
23-valent vaccine has been available in Canada and this covers 85% of the serotypes responsible for invasive pneumococcal
infection. Use of this vaccine in elderly patients with chronic
lung disease revealed a significant lower risk for pneumonia,
hospitalization and death, and direct medical care cost savings
(329). However, AECB is a mucosal infection and it is unclear
whether this vaccine can reduce the incidence of this complication of chronic bronchitis. Some reports state that the vaccine has up to a 65% efficacy in patients with COPD but do
not specifically comment on AECB (329). It is generally
agreed that pneumococcal vaccination is safe and can reduce
invasive pneumococcal infection leading to current recommendations for vaccinations in all patients with COPD at least
once in their lives. In addition, consideration should be given
to repeating the vaccine in five to 10 years in high-risk
patients (330) (Level III evidence).
Over the past two decades, attempts have been made to use
oral administration of bacterial antigens in the hope of upregulating antigen-specific antibodies in the bronchial mucosa,
thereby decreasing the frequency of AECB. Initial studies
using an oral vaccine against H influenzae revealed a decrease
of approximately 50% in use of antibiotics and days lost from
work in patients with chronic bronchitis (331). A recent
meta-analysis of six trials using this vaccine showed a decrease
in the number of episodes of bronchitis at both three and six
months in treated patients and a decrease in antibiotic use at
six months but not at three months in treated patients (332).
Problems with this meta-analysis include the fact that some
patients with recurrent episodes of acute bronchitis and without underlying chronic bronchitis were included. In addition,
a six-month follow-up only was obtained, so it is unclear
whether there will be a continued benefit at one or two years
after vaccination. More recent studies have used a preparation
called OM-85, which is a lyophilized powder made from cultures of eight different bacterial pathogens responsible for
AECB (H influenzae, S pneumoniae, M catarrhalis, K pneumoniae,
22B
Klebsiella ozaenae, S aureus, Streptococcus pyogenes and
Streptococcus viridans). The use of this preparation in institutionalized elderly patients with chronic bronchitis led to a 30%
reduction in respiratory tract infections (333). However, a
more recent multicentre study failed to demonstrate any reduction in the frequency of AECB (334). Nonetheless, patients
treated with the vaccine had a 30% reduction in hospitalization related to respiratory problems and a 55% reduction in
total number of days in hospital. A more recent analysis of this
study suggested that use of this oral immunostimulating agent
was cost effective (335). If available in the future, the use of
oral immunostimulating agents would be recommended in
Canada (Level II evidence).
The use of inhaled corticosteroids in chronic bronchitis and
COPD has been the subject of great interest over the past
decade. There are two potential mechanisms whereby inhaled
steroids might have a role in chronic bronchitis. First, by
decreasing the annual rate of decline in FEV1 which is the
major predictor of mortality from COPD. Second, by decreasing airway inflammation via an effect on either mucus hypersecretion or on inflammatory cytokines and mediators.
Theoretically, this effect should decrease the risk of exacerbations. Studies examining the effects of inhaled steroids on airway inflammation have been conflicting. There is some
evidence that therapy with higher doses of inhaled corticosteroids reduces visible bronchial inflammation and epithelial
fluid albumin (336), airway neutrophilia (337) and markers of
neutrophilic inflammation such as IL-8 and MPO (338). A
similar number of studies failed to demonstrate any effect of
inhaled steroids on airway neutrophilia, epithelial permeability
or airway mediator and cytokine levels (339-341). Patients in
studies showing a beneficial response tended to be treated for
somewhat longer periods of time (six to eight weeks versus four
weeks), but it is unclear whether this is a sufficient explanation
for the different outcomes.
The past two years have brought with them the publication
of long awaited trials of the effects of inhaled corticosteroids in
slowing the rate of annual decline of FEV1 in patients with
COPD. These studies examined the effects of different inhaled
steroids (budesonide, fluticasone propionate, triamcinolone)
versus placebo for 3 to 3.5 years with a total of over 3000
patients completing the trials (342-345). Overall, there was no
benefit seen in terms of rate of decline in lung function in
patients treated with inhaled steroids versus those getting
placebo. In addition, patients receiving inhaled steroids had a
higher percentage of skin bruising (342), a decrease in bone
density of the lumbar spine and femur (345) and a small
decrease in mean cortisol concentrations, although this was
not associated with any clinical effects (344).
The Inhaled Steroids on Obstructive Lung Disease in
Europe (ISOLDE) study (344) revealed a 25% reduction in
the median exacerbation rate from 1.32 per year on placebo
to 0.99 per year for patients on fluticasone propionate.
Another study examining the effects of fluticasone 500 µg
twice daily versus placebo over the course of six months also
showed a significant reduction in both moderate and severe
exacerbations in the steroid-treated group compared with the
placebo group (86% versus 60%, P<0.001) (346). Available
data do not allow specific recommendations to be made
regarding the use of inhaled steroids in patients with COPD.
The risks versus the benefits of this therapy must be individualized. Patients with severe impairment in FEV1 and those
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with frequent exacerbations requiring the use of oral corticosteroids should be considered for therapy with inhaled
corticosteroids (Level III evidence). Supporting this recommendation is a recent cohort study performed in Ontario.
Data were collected regarding filling of prescriptions for
inhaled steroids in 22,620 patients over the age of 65 years
hospitalized with COPD, and one-year prognosis was measured according to whether they received a prescription for an
inhaled steroid within three months of their admission.
Prescription of an inhaled steroid led to a 10% one-year
reduction in readmission and/or death (347). After adjusting
for age, sex, comorbid conditions, concomitant medications
and visits for COPD in the preceding year, the reduction in
mortality was 29% (95% CI, 22% to 35%) and reduction in
risk of readmission was 24% (95% CI, 22% to 29%) (347).
There is little evidence to suggest a benefit of regular therapy
with oral corticosteroids in patients with COPD. Although
two retrospective, long term studies (348,349) claimed to
demonstrate a beneficial effect over 20 years in patients with
COPD, this effect was most apparent in patients with the most
rapid rate of decline in FEV1 and no comments were made on
the frequency of AECB. The same group showed no benefit
with the addition of 5 mg of prednisolone daily to inhaled
corticosteroids in patients with relatively mild COPD in terms
of decreasing the frequency or duration of AECB over a twoyear period (350). This, combined with the recognition of the
significant complications of chronic oral corticosteroid therapy (351,352) including a dose-dependent increase in mortality
(353), argues against chronic use of systemic steroids in COPD
(Level II evidence). It appears that even patients on chronic
oral corticosteroids can be weaned off this medication without
any adverse effects on pulmonary function, quality of life or
frequency of AECB (354).
Long-acting beta-agonists have been shown to be beneficial in some patients with COPD. Some evidence exists that
salmeterol is effective in reducing damage to the epithelium
caused by H influenzae or P aeruginosa in vitro (355,356).
Theoretically, this may lead to less epithelial damage caused
by bacteria and reduce the frequency or severity of AECB.
There is some early clinical evidence that this may be true
with patients on salmeterol having a longer time to first
AECB compared to placebo or ipratropium (357). A similar
delay in time to next exacerbation has recently been demonstrated in patients prescribed tiotropium (358,359). Further
investigations will be necessary before long-acting betaagonists or long-acting anticholinergics can be recommended
for this purpose.
A meta-analysis published in 1998 suggested that oral
mucolytic agents such as N-acetylcysteine or iodinated glycerol reduced the frequency of AECB, disability days and
antibiotic use (360). The greatest effects were seen in
patients who had a large number of exacerbations. Oral
mucolytic agents reduced exacerbations by 22% in patients
who had an average of 5.5 exacerbations per year. However, a
more typical chronic bronchitic patient with two to three
exacerbations per year would expect to reduce exacerbations
by less than one by taking mucolytic agents daily for two to
three years. No effect on rate of decline of FEV1 was seen. A
more recent meta-analysis on the effect of oral N-acetylcysteine
revealed similar results in terms of a decrease in AECB in
patients treated for 12 to 24 weeks (361). In addition, a recently published update of Poole’s Cochrane analysis confirmed the
Can Respir J Vol 10 Suppl B July/August 2003
beneficial results of N-acetylcysteine and determined that
the number of patients needed to treat for one patient to
have no exacerbations during the study period was six (362).
A study in Switzerland suggested that therapy with N-acetylcysteine was cost effective (363). The mechanism by which
N-acetylcysteine reduces AECB is unclear but may be related
to enhancing macrophage activity, which would help defend
against mucosal infections (364). N-acetylcysteine therapy
should be considered in patients with more than five exacerbations per year (Level I evidence).
Hyaluronan is a high molecular weight glycosaminoglycan
that is found naturally in the body. It has a role in enhancing
neutrophil function. It has been shown to significantly
decrease the frequency of AECB and reduce the need for
antibiotics in this group of patients (365). It has to be given
by subcutaneous injection weekly, making it somewhat
impractical. In addition, cost effectiveness of this form of
therapy remains to be proven. At this point, its use cannot be
endorsed to prevent AECB (Level III evidence).
Numerous trials dating back to the mid-1950s have been
carried out to determine whether antibiotic prophylaxis
reduces the frequency of AECB (93,366,367). Murphy and
Sethi (93) identified nine prospective, placebo-controlled,
randomized trials in each of which at least 25 patients were
studied. In five of these trials, no reduction in the frequency
of exacerbations was achieved; however, in two of these,
significantly less time was lost from work by the antibiotictreated groups (368,369). In four studies, the frequency of
AECB was significantly reduced in groups treated with
antibiotics compared with those receiving placebo. Similar to
studies using other agents that decrease airway inflammation,
antibiotic prophylaxis seemed to benefit patients who suffered the largest number of exacerbations over the course of
the year. Therefore, patients in group III may benefit from
prophylaxis with antibiotic agents to which their colonizing
bacteria are sensitive. It should be pointed out that each of
these studies regarding antibiotic prophylaxis was done with
older generations of antibiotics and there is a need for current
studies with newer antibiotics, particularly given the emerging bacterial resistance problems. Nonetheless, the effects of
the antibiotics may be anti-inflammatory rather than antimicrobial. This is suggested by a recent study looking at the
effects of erythromycin versus placebo in preventing AECB
and hospitalizations in patients with COPD. Erythomycin
has no significant activity against H influenzae, the most
important pathogen in AECB, yet therapy with 200 mg/day
to 400 mg/day of erythromycin for one year led to a 4.71
decrease in the relative risk of developing AECB (11% versus
56% in the placebo group) and a significant decrease in hospitalizations due to AECB (370).
Overall, there is evidence to support antibiotic prophylaxis
in patients with frequent exacerbations (Level II evidence).
However, decisions regarding prophylactic antibiotic treatment should be made on an individual basis.
THE FUTURE
The past decade has brought with it renewed interest into the
pathogenesis of chronic bronchitis and a greater understanding of some of the basic mechanisms of the disease.
Paradoxically, these discoveries have brought with them more
questions. To improve our therapy of AECB, we need better
evidence on which to base future guidelines. The following
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Balter et al
are the issues most urgently in need of answers in order to
make future AECB guidelines more evidence based:
1. We need a better definition of AECB to help guide
the design of clinical trials, to allow the results to be
generalizable and to better determine the health and
economic impact of exacerbations.
groups II or III but would be reasonable for patients
with an Anthonisen type II or III exacerbations or for
patients in our stratification group I.
5. A study examining the potential role for prophylactic
antibiotics for patients in our stratification group III
would be welcome.
2. Antibiotic trials that compare different classes of drugs
powered to show superiority of one class over another
are desperately needed to make evidence-based
recommendations regarding drugs of first choice for
AECB.
3. The importance of bacterial eradication in terms of
both symptom resolution and determination of
remission-free period requires further study.
4. The importance of reducing airway inflammation
either with antibiotics with anti-inflammatory effects
or with novel anti-inflammatory agents must be
studied prospectively in a controlled trial. Ideally, a
study looking at the effects of oral steroids alone
without concomitant antibiotics should be carried out.
This may be ethically difficult to do in patients with
Anthonisen type I exacerbations stratified to our
6. We need better surrogate markers for bacterial
infections. A better understanding of the antigenic
structures of many of the common bacteria involved in
AECB might lead to the development of monoclonal
antibodies targeted against these antigens, which may
help define acute bacterial infections.
ACKNOWLEDGEMENTS: We gratefully acknowledge the
contribution and input in reviewing earlier versions of this manuscript of Dr Michael S Niederman, Winthrop University Hospital,
Mineola New York; Dr G Douglas Campbell, LSU Medical
Center, Shrevport, Louisiana; Dr Marc Miravitlles, Hospital
General Universitarivall d’Hebron, Barcelona, Spain; and
Dr Robert Wilson-Royal, Brompton Hospital, London, England.
Preparation of this manuscript was coordinated by Core Health
Services Inc. This study was sponsored by unrestricted educational grants from Abbott Laboratories Limited, Bayer Inc, BristolMyers Squibb Canada Inc, GlaxoSmithKline, Janssen-Ortho Inc
and Pfizer Canada Inc.
APPENDIX
Chronic Bronchitis Working Group
Antonio Anzueto MD, University of Texas, San Antonio, Texas, USA; Abraham Born MD, FRCPC, North York General Hospital
and University of Toronto, Toronto, Ontario; Jacques Bouchard MD, St-Joseph’s Hospital, La Malbaie, Quebec; Nigel JD Duguid
MB, FRCPC, Memorial University, Health Care Corporation of St John’s, St John’s, Newfoundland; Godfrey Harding MD, FACP,
FRCPC, University of Manitoba, St Boniface General Hospital, Winnipeg, Manitoba; Marcel Julien MD, FRCPC, Hopital du
Sacre-Coeur, Montreal, Quebec; Noel Lampron MD, Université Laval, Laval Hospital, Ste Foy, Quebec; Robert D Levy MD,
FRCPC, Univesity of British Columbia, Vancouver General Hospital, Vancouver, British Columbia; James A McSherry MB, ChB,
FCFP, FRCGP, FRCP Glasg, FAMB, University of Western Ontario, London Health Sciences Centre, London, Ontario; Karl A
Weiss MD, MSc, FRCPC, University of Montreal, Hôpital Maisonneuve-Rosemont, Montreal, Quebec.
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Can Respir J Vol 10 Suppl B July/August 2003